old_contents: # -*- coding: utf-8 -*-
  from __future__ import absolute_import
  from solidspy.solids_GUI import solids_GUI
  
  __all__ = ["assemutil",
             "femutil",
             "gaussutil",
             "postprocesor",
             "preprocesor",
             "solutil",
             "uelutil",
             "solids_GUI"]
  
new_contents: # -*- coding: utf-8 -*-
  from __future__ import absolute_import
  from solidspy.solids_GUI import solids_GUI
  
  __all__ = ["assemutil",
             "femutil",
             "gaussutil",
             "postprocesor",
             "preprocesor",
             "solutil",
             "uelutil",
             "solids_GUI"]
  
  
  __citation__ = """@software{solidspy,
   title = {SolidsPy: 2D-Finite Element Analysis with Python},
   author = {Gómez, Juan and Guarín-Zapata, Nicolás},
   year = 2018,
   keywords = {Python, Computer algebra system, Symbolics},
   abstract = {SolidsPy is a simple finite element analysis code for
     2D elasticity problems. The code uses as input simple-to-create text
     files defining a model in terms of nodal, element, material and
     load data.},
   url = {https://github.com/AppliedMechanics-EAFIT/SolidsPy}
  }"""
  
subject: Add citation to __init__.py