diff --git a/imagine/__init__.py b/imagine/__init__.py
index 306b36d45079b68eef9d9f074024fd3aa06ab408..dc303cbfe4dd04d9453680527c5dd7a1e7ead55c 100644
--- a/imagine/__init__.py
+++ b/imagine/__init__.py
@@ -1,21 +1,3 @@
-# This program is free software: you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation, either version 3 of the License, or
-# (at your option) any later version.
-#
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
-#
-# Copyright(C) 2013-2017 Max-Planck-Society
-#
-# IMAGINE is being developed at the Max-Planck-Institut fuer Astrophysik
-# and financially supported by the Studienstiftung des deutschen Volkes.
-
 from .version import __version__
 
 from likelihoods import *
diff --git a/imagine/likelihoods/__init__.py b/imagine/likelihoods/__init__.py
index 00113783fd5a353158799490ea022b54358559cc..8f127c96fc05acd88eae95651de22a875cac0b2b 100644
--- a/imagine/likelihoods/__init__.py
+++ b/imagine/likelihoods/__init__.py
@@ -1,21 +1,3 @@
-# This program is free software: you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation, either version 3 of the License, or
-# (at your option) any later version.
-#
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
-#
-# Copyright(C) 2013-2017 Max-Planck-Society
-#
-# IMAGINE is being developed at the Max-Planck-Institut fuer Astrophysik
-# and financially supported by the Studienstiftung des deutschen Volkes.
-
-from likelihood import Likelihood
-from ensemble_likelihood import *
-from simple_likelihood import SimpleLikelihood
+from .likelihood import Likelihood
+from .ensemble_likelihood import EnsemleLikelihood
+from .simple_likelihood import SimpleLikelihood
diff --git a/imagine/likelihoods/ensemble_likelihood/ensemble_likelihood.py b/imagine/likelihoods/ensemble_likelihood.py
similarity index 98%
rename from imagine/likelihoods/ensemble_likelihood/ensemble_likelihood.py
rename to imagine/likelihoods/ensemble_likelihood.py
index 00447635d080df72d236bf57f5d550f6ac519b97..33e800cd6ed533a83f210b14836b01c503e4c0d9 100644
--- a/imagine/likelihoods/ensemble_likelihood/ensemble_likelihood.py
+++ b/imagine/likelihoods/ensemble_likelihood.py
@@ -17,10 +17,8 @@
 # and financially supported by the Studienstiftung des deutschen Volkes.
 
 import numpy as np
-
-from nifty import Field
-
-from imagine.likelihoods.likelihood import Likelihood
+from nifty4 import Field
+from .likelihood import Likelihood
 
 
 class EnsembleLikelihood(Likelihood):
diff --git a/imagine/likelihoods/ensemble_likelihood/__init__.py b/imagine/likelihoods/ensemble_likelihood/__init__.py
deleted file mode 100644
index ec45a385578b93748383cd2431c065860cc6bc46..0000000000000000000000000000000000000000
--- a/imagine/likelihoods/ensemble_likelihood/__init__.py
+++ /dev/null
@@ -1,19 +0,0 @@
-# This program is free software: you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation, either version 3 of the License, or
-# (at your option) any later version.
-#
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
-#
-# Copyright(C) 2013-2017 Max-Planck-Society
-#
-# IMAGINE is being developed at the Max-Planck-Institut fuer Astrophysik
-# and financially supported by the Studienstiftung des deutschen Volkes.
-
-from ensemble_likelihood import EnsembleLikelihood
diff --git a/imagine/likelihoods/likelihood/likelihood.py b/imagine/likelihoods/likelihood.py
similarity index 86%
rename from imagine/likelihoods/likelihood/likelihood.py
rename to imagine/likelihoods/likelihood.py
index cb988f232db164a10430364771a7f55b124c66c6..903cde0ee327d81747827f5aef2e1a5b0b75a4d0 100644
--- a/imagine/likelihoods/likelihood/likelihood.py
+++ b/imagine/likelihoods/likelihood.py
@@ -17,10 +17,7 @@
 # and financially supported by the Studienstiftung des deutschen Volkes.
 
 import abc
-
-from keepers import Loggable
-
-from nifty import FieldArray
+import nifty4 as ift
 
 
 class Likelihood(Loggable, object):
@@ -29,12 +26,12 @@ class Likelihood(Loggable, object):
         raise NotImplementedError
 
     def _strip_data(self, data):
-        # if the first element in the domain tuple is a FieldArray we must
+        # if the first element in the domain tuple is unstructured, we must
         # extract the data
         if not hasattr(data, 'domain'):
             return data
 
-        if isinstance(data.domain[0], FieldArray):
+        if isinstance(data.domain[0], ift.UnstructuredDomain):
             data = data.val.get_full_data()[0]
         else:
             data = data.val.get_full_data()
diff --git a/imagine/likelihoods/likelihood/__init__.py b/imagine/likelihoods/likelihood/__init__.py
deleted file mode 100644
index 8921774c72618eb27cf35bf540127838df4f2c9b..0000000000000000000000000000000000000000
--- a/imagine/likelihoods/likelihood/__init__.py
+++ /dev/null
@@ -1,19 +0,0 @@
-# This program is free software: you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation, either version 3 of the License, or
-# (at your option) any later version.
-#
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
-#
-# Copyright(C) 2013-2017 Max-Planck-Society
-#
-# IMAGINE is being developed at the Max-Planck-Institut fuer Astrophysik
-# and financially supported by the Studienstiftung des deutschen Volkes.
-
-from likelihood import Likelihood
diff --git a/imagine/likelihoods/simple_likelihood/simple_likelihood.py b/imagine/likelihoods/simple_likelihood.py
similarity index 100%
rename from imagine/likelihoods/simple_likelihood/simple_likelihood.py
rename to imagine/likelihoods/simple_likelihood.py
diff --git a/imagine/likelihoods/simple_likelihood/__init__.py b/imagine/likelihoods/simple_likelihood/__init__.py
deleted file mode 100644
index 8db1d0621aeaa3826d80e4b486a04c0dd655c86d..0000000000000000000000000000000000000000
--- a/imagine/likelihoods/simple_likelihood/__init__.py
+++ /dev/null
@@ -1,19 +0,0 @@
-# This program is free software: you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation, either version 3 of the License, or
-# (at your option) any later version.
-#
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
-#
-# Copyright(C) 2013-2017 Max-Planck-Society
-#
-# IMAGINE is being developed at the Max-Planck-Institut fuer Astrophysik
-# and financially supported by the Studienstiftung des deutschen Volkes.
-
-from simple_likelihood import SimpleLikelihood
diff --git a/imagine/magnetic_fields/__init__.py b/imagine/magnetic_fields/__init__.py
index 8baf87845c78def488aa27e5398a381935412f3c..0a9bf1de770a96407fe36ac97783e91701c30d1f 100644
--- a/imagine/magnetic_fields/__init__.py
+++ b/imagine/magnetic_fields/__init__.py
@@ -1,21 +1,3 @@
-# This program is free software: you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation, either version 3 of the License, or
-# (at your option) any later version.
-#
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
-#
-# Copyright(C) 2013-2017 Max-Planck-Society
-#
-# IMAGINE is being developed at the Max-Planck-Institut fuer Astrophysik
-# and financially supported by the Studienstiftung des deutschen Volkes.
-
 from magnetic_field import MagneticField, \
                            MagneticFieldFactory
 
diff --git a/imagine/magnetic_fields/constant_magnetic_field/constant_magnetic_field.py b/imagine/magnetic_fields/constant_magnetic_field/constant_magnetic_field.py
index 73e5319ff4b8792fe6692bc12707a5ea70bc858c..ab2a9c0f871ea50ce400e7ee15d89a746f3cdde2 100644
--- a/imagine/magnetic_fields/constant_magnetic_field/constant_magnetic_field.py
+++ b/imagine/magnetic_fields/constant_magnetic_field/constant_magnetic_field.py
@@ -22,8 +22,7 @@ from imagine.magnetic_fields.magnetic_field import MagneticField
 class ConstantMagneticField(MagneticField):
     @property
     def parameter_list(self):
-        parameter_list = ['b_x', 'b_y', 'b_z']
-        return parameter_list
+        return ['b_x', 'b_y', 'b_z']
 
     def _create_field(self):
         val = self.cast(None)
diff --git a/imagine/magnetic_fields/constant_magnetic_field/constant_magnetic_field_factory.py b/imagine/magnetic_fields/constant_magnetic_field/constant_magnetic_field_factory.py
index f41a770d0986575d170f7c3e8116167c05727df9..726a9fa8115865f8dc172c41fe425c6f27a3c719 100644
--- a/imagine/magnetic_fields/constant_magnetic_field/constant_magnetic_field_factory.py
+++ b/imagine/magnetic_fields/constant_magnetic_field/constant_magnetic_field_factory.py
@@ -31,10 +31,7 @@ class ConstantMagneticFieldFactory(MagneticFieldFactory):
 
     @property
     def _initial_parameter_defaults(self):
-        defaults = {'b_x': 0,
-                    'b_y': 0,
-                    'b_z': 0}
-        return defaults
+        return dict(b_x=0, b_y=0, b_z=0)
 
     @property
     def _initial_variable_to_parameter_mappings(self):
diff --git a/imagine/magnetic_fields/magnetic_field/__init__.py b/imagine/magnetic_fields/magnetic_field/__init__.py
index 3b78db48eca19210acebca7be9d04948cd959a5d..5faeff26075d118639fe993b8fb53b8227b86d2c 100644
--- a/imagine/magnetic_fields/magnetic_field/__init__.py
+++ b/imagine/magnetic_fields/magnetic_field/__init__.py
@@ -1,20 +1,2 @@
-# This program is free software: you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation, either version 3 of the License, or
-# (at your option) any later version.
-#
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
-#
-# Copyright(C) 2013-2017 Max-Planck-Society
-#
-# IMAGINE is being developed at the Max-Planck-Institut fuer Astrophysik
-# and financially supported by the Studienstiftung des deutschen Volkes.
-
 from magnetic_field import MagneticField
 from magnetic_field_factory import MagneticFieldFactory
diff --git a/imagine/magnetic_fields/wmap3yr_magnetic_field/__init__.py b/imagine/magnetic_fields/wmap3yr_magnetic_field/__init__.py
index 79a721e42703a3098187d2da4b1d222ef61da181..e57e9bd18c826236f0026f21ddea1d7b9fe59a37 100644
--- a/imagine/magnetic_fields/wmap3yr_magnetic_field/__init__.py
+++ b/imagine/magnetic_fields/wmap3yr_magnetic_field/__init__.py
@@ -1,20 +1,2 @@
-# This program is free software: you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation, either version 3 of the License, or
-# (at your option) any later version.
-#
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
-#
-# Copyright(C) 2013-2017 Max-Planck-Society
-#
-# IMAGINE is being developed at the Max-Planck-Institut fuer Astrophysik
-# and financially supported by the Studienstiftung des deutschen Volkes.
-
 from wmap3yr_magnetic_field import WMAP3yrMagneticField
 from wmap3yr_magnetic_field_factory import WMAP3yrMagneticFieldFactory
diff --git a/imagine/observables/__init__.py b/imagine/observables/__init__.py
index cb2e83dcbbc6af685c545def43d8bf1e0365f360..2f5b18d28707727dd04dab0bf14c65dd2a2219b2 100644
--- a/imagine/observables/__init__.py
+++ b/imagine/observables/__init__.py
@@ -1,19 +1 @@
-# This program is free software: you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation, either version 3 of the License, or
-# (at your option) any later version.
-#
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
-#
-# Copyright(C) 2013-2017 Max-Planck-Society
-#
-# IMAGINE is being developed at the Max-Planck-Institut fuer Astrophysik
-# and financially supported by the Studienstiftung des deutschen Volkes.
-
 from observable import Observable
diff --git a/imagine/observers/__init__.py b/imagine/observers/__init__.py
index 38f768baf830709b2e28651a29cdc7cbb6644175..74cb35fadfc9cad6689c9b69b10fe0458debaa93 100644
--- a/imagine/observers/__init__.py
+++ b/imagine/observers/__init__.py
@@ -1,20 +1,2 @@
-# This program is free software: you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation, either version 3 of the License, or
-# (at your option) any later version.
-#
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
-#
-# Copyright(C) 2013-2017 Max-Planck-Society
-#
-# IMAGINE is being developed at the Max-Planck-Institut fuer Astrophysik
-# and financially supported by the Studienstiftung des deutschen Volkes.
-
 from observer import Observer
 from hammurapy import *
diff --git a/imagine/observers/hammurapy/__init__.py b/imagine/observers/hammurapy/__init__.py
index 2308be8416862830e62460c0e039d1fa1f35bb3b..ce7ea6e441efeb7af67401674c23afce5da5a076 100644
--- a/imagine/observers/hammurapy/__init__.py
+++ b/imagine/observers/hammurapy/__init__.py
@@ -1,21 +1,3 @@
-# This program is free software: you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation, either version 3 of the License, or
-# (at your option) any later version.
-#
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
-#
-# Copyright(C) 2013-2017 Max-Planck-Society
-#
-# IMAGINE is being developed at the Max-Planck-Institut fuer Astrophysik
-# and financially supported by the Studienstiftung des deutschen Volkes.
-
 from observable_mixins import *
 from model_mixins import *
 from hammurapy import Hammurapy
diff --git a/imagine/observers/hammurapy/model_mixins/__init__.py b/imagine/observers/hammurapy/model_mixins/__init__.py
index bce6faee351bbde2bf0be3557b316b1e5d4cce18..b51cb07832512b6c13f615a9ea918082549332f6 100644
--- a/imagine/observers/hammurapy/model_mixins/__init__.py
+++ b/imagine/observers/hammurapy/model_mixins/__init__.py
@@ -1,20 +1,2 @@
-# This program is free software: you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation, either version 3 of the License, or
-# (at your option) any later version.
-#
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
-#
-# Copyright(C) 2013-2017 Max-Planck-Society
-#
-# IMAGINE is being developed at the Max-Planck-Institut fuer Astrophysik
-# and financially supported by the Studienstiftung des deutschen Volkes.
-
 from magnetic_field_model import MagneticFieldModel
 from wmap3yr_mixin import WMAP3yrMixin
diff --git a/imagine/observers/hammurapy/observable_mixins/__init__.py b/imagine/observers/hammurapy/observable_mixins/__init__.py
index 64c4ae5445bb163fd402e314872806c0175949a4..eddcb686cdd4a574281e279e290bc019f632526a 100644
--- a/imagine/observers/hammurapy/observable_mixins/__init__.py
+++ b/imagine/observers/hammurapy/observable_mixins/__init__.py
@@ -1,21 +1,3 @@
-# This program is free software: you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation, either version 3 of the License, or
-# (at your option) any later version.
-#
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
-#
-# Copyright(C) 2013-2017 Max-Planck-Society
-#
-# IMAGINE is being developed at the Max-Planck-Institut fuer Astrophysik
-# and financially supported by the Studienstiftung des deutschen Volkes.
-
 from observable_mixin import ObservableMixin
 from dm_mixin import DMMixin
 from fd_mixin import FDMixin
diff --git a/imagine/observers/observer/observer.py b/imagine/observers/observer.py
similarity index 100%
rename from imagine/observers/observer/observer.py
rename to imagine/observers/observer.py
diff --git a/imagine/observers/observer/__init__.py b/imagine/observers/observer/__init__.py
deleted file mode 100644
index fb2a219b2ee4974e5e79d2cbffe7329dea87097a..0000000000000000000000000000000000000000
--- a/imagine/observers/observer/__init__.py
+++ /dev/null
@@ -1,19 +0,0 @@
-# This program is free software: you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation, either version 3 of the License, or
-# (at your option) any later version.
-#
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
-#
-# Copyright(C) 2013-2017 Max-Planck-Society
-#
-# IMAGINE is being developed at the Max-Planck-Institut fuer Astrophysik
-# and financially supported by the Studienstiftung des deutschen Volkes.
-
-from observer import Observer
diff --git a/imagine/priors/__init__.py b/imagine/priors/__init__.py
index 26395c0ff85081c4068f3b10b09e1a371d28c758..aca949cc0eed92ead01e9d23f17d8cc2376e4748 100644
--- a/imagine/priors/__init__.py
+++ b/imagine/priors/__init__.py
@@ -1,20 +1,2 @@
-# This program is free software: you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation, either version 3 of the License, or
-# (at your option) any later version.
-#
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
-#
-# Copyright(C) 2013-2017 Max-Planck-Society
-#
-# IMAGINE is being developed at the Max-Planck-Institut fuer Astrophysik
-# and financially supported by the Studienstiftung des deutschen Volkes.
-
-from prior import Prior
-from flat_prior import FlatPrior
+from .prior import Prior
+from .flat_prior import FlatPrior
diff --git a/imagine/priors/flat_prior/flat_prior.py b/imagine/priors/flat_prior.py
similarity index 100%
rename from imagine/priors/flat_prior/flat_prior.py
rename to imagine/priors/flat_prior.py
diff --git a/imagine/priors/flat_prior/__init__.py b/imagine/priors/flat_prior/__init__.py
deleted file mode 100644
index 4b168641896354d7bf6b3ae64cdb364b8f7b99a5..0000000000000000000000000000000000000000
--- a/imagine/priors/flat_prior/__init__.py
+++ /dev/null
@@ -1,19 +0,0 @@
-# This program is free software: you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation, either version 3 of the License, or
-# (at your option) any later version.
-#
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
-#
-# Copyright(C) 2013-2017 Max-Planck-Society
-#
-# IMAGINE is being developed at the Max-Planck-Institut fuer Astrophysik
-# and financially supported by the Studienstiftung des deutschen Volkes.
-
-from flat_prior import FlatPrior
diff --git a/imagine/priors/prior/prior.py b/imagine/priors/prior.py
similarity index 100%
rename from imagine/priors/prior/prior.py
rename to imagine/priors/prior.py
diff --git a/imagine/priors/prior/__init__.py b/imagine/priors/prior/__init__.py
deleted file mode 100644
index 1635edc7650514c5253f917c894e4bb51a3805ba..0000000000000000000000000000000000000000
--- a/imagine/priors/prior/__init__.py
+++ /dev/null
@@ -1,19 +0,0 @@
-# This program is free software: you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation, either version 3 of the License, or
-# (at your option) any later version.
-#
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
-#
-# Copyright(C) 2013-2017 Max-Planck-Society
-#
-# IMAGINE is being developed at the Max-Planck-Institut fuer Astrophysik
-# and financially supported by the Studienstiftung des deutschen Volkes.
-
-from prior import Prior
diff --git a/imagine/pymultinest_importer/__init__.py b/imagine/pymultinest_importer/__init__.py
index d2d1ae6eacc7b4c2d08543ee855cd3337acceab9..625f5b300efbe3a4e9e256c28e515597397eaed5 100644
--- a/imagine/pymultinest_importer/__init__.py
+++ b/imagine/pymultinest_importer/__init__.py
@@ -1,19 +1 @@
-# This program is free software: you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation, either version 3 of the License, or
-# (at your option) any later version.
-#
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
-#
-# Copyright(C) 2013-2017 Max-Planck-Society
-#
-# IMAGINE is being developed at the Max-Planck-Institut fuer Astrophysik
-# and financially supported by the Studienstiftung des deutschen Volkes.
-
 from pymultinest_importer import pymultinest
diff --git a/setup.py b/setup.py
index 67b23093120df3b12e84f7f7380eaa61075827df..a919e6f492db42c85d2980170f5aad01ee3829af 100644
--- a/setup.py
+++ b/setup.py
@@ -41,8 +41,8 @@ setup(name = "imagine",
       package_data={'imagine.observers.hammurapy': ['input/*'],},
       package_dir={"imagine": "imagine"},
       dependency_links=[
-        'git+https://gitlab.mpcdf.mpg.de/ift/nifty.git/@NIFTy_3#egg=ift_nifty-3.0.3'],
-      install_requires=['ift_nifty>=3.0.3', 'simplejson'],
+        'git+https://gitlab.mpcdf.mpg.de/ift/nifty.git/#egg=nifty4-4.2.0'],
+      install_requires=['nifty4>=4.2.0', 'simplejson'],
       zip_safe=False,
       classifiers=[
          "Development Status :: 4 - Beta",