diff --git a/examples/problems/burgers.py b/examples/problems/burgers.py
index 56c06fb..4e143f2 100644
--- a/examples/problems/burgers.py
+++ b/examples/problems/burgers.py
@@ -15,7 +15,8 @@ class Burgers1D(TimeDependentProblem, SpatialProblem):
 
     def burger_equation(input_, output_):
         grad_u = grad(output_['u'], input_)
-        grad_x, grad_t = grad(output_['u'], input_).T
+        grad_x = grad_u['x']
+        grad_t = grad_u['t']
         gradgrad_u_x = grad(grad_u['x'], input_)
         return (
             grad_u['t'] + output_['u']*grad_u['x'] -
diff --git a/examples/run_burgers.py b/examples/run_burgers.py
index 2363561..7bf8ba8 100644
--- a/examples/run_burgers.py
+++ b/examples/run_burgers.py
@@ -37,7 +37,7 @@ if __name__ == "__main__":
         output_variables=burgers_problem.output_variables,
         input_variables=burgers_problem.input_variables,
         func=Softplus,
-        extra_features=feat
+        extra_features=feat,
     )
 
     pinn = PINN(
diff --git a/examples/run_poisson.py b/examples/run_poisson.py
index 055503a..a6fea52 100644
--- a/examples/run_poisson.py
+++ b/examples/run_poisson.py
@@ -1,17 +1,14 @@
+import argparse
 import sys
 import numpy as np
 import torch
-import argparse
-from pina import PINN
-from pina.ppinn import ParametricPINN as pPINN
-from pina.label_tensor import LabelTensor
 from torch.nn import ReLU, Tanh, Softplus
-from problems.poisson2D import Poisson2D
-from pina.deep_feed_forward import DeepFeedForward
 
+from pina import PINN, LabelTensor, Plotter
+from pina.model import FeedForward
 from pina.adaptive_functions import AdaptiveSin, AdaptiveCos, AdaptiveTanh
+from problems.poisson import Poisson
 
-from pina import Plotter
 
 class myFeature(torch.nn.Module):
     """
@@ -36,8 +33,8 @@ if __name__ == "__main__":
 
     feat = [myFeature()] if args.features else []
 
-    poisson_problem = Poisson2D()
-    model = DeepFeedForward(
+    poisson_problem = Poisson()
+    model = FeedForward(
         layers=[10, 10],
         output_variables=poisson_problem.output_variables,
         input_variables=poisson_problem.input_variables,
diff --git a/pina/plotter.py b/pina/plotter.py
index ff14e76..15add45 100644
--- a/pina/plotter.py
+++ b/pina/plotter.py
@@ -1,6 +1,6 @@
 """ Module for plotting. """
 import matplotlib
-matplotlib.use('Qt5Agg')
+#matplotlib.use('Qt5Agg')
 import matplotlib.pyplot as plt
 import numpy as np
 import torch
diff --git a/setup.py b/setup.py
index 3dabfd6..e9370e6 100644
--- a/setup.py
+++ b/setup.py
@@ -14,7 +14,8 @@ VERSION = meta['__version__']
 KEYWORDS = 'physics-informed neural-network'
 
 REQUIRED = [
-    'future', 'numpy', 'matplotlib', 'torch'
+    'future', 'numpy', 'matplotlib', 'torch', 'mpmath'
+    
 ]
 
 EXTRAS = {