Copyright

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                   | |                     OpenFree Finite Element                   
                   |_|                         and Discrete Element Method Solver    
                                                                                     
        OpenFDEM : Object Oriented Open Free Finite Discrete Element Code   
                                                                                     

            Copyright (C) 2017 - 2022   Xiaofeng Li                                  
                         Email: xfli@whrsm.ac.cn                                     
                                                                                     
     OpenFDEM Project Website: https://xiaofengli-uoft.github.io/
         Geomechanics Group Website: https://geogroup.utoronto.ca/
         
     This library is free software; you can redistribute it and/or                   
     modify it under the terms of the GNU Lesser General Public                      
     License as published by the Free Software Foundation; either                    
     version 2.1 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               
     Lesser General Public License for more details.