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References
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* GitHub: `<https://github.com/CFDEMproject/LIGGGHTS-PUBLIC>`_
* User manual: `<https://www.cfdem.com/media/DEM/docu/Manual.html>`_
* Website: `<http://www.cfdem.com>`_
* Commercial version (Aspherix): `<https://www.aspherix-dem.com/>`_