How to cite LigDig
You are free to use LigDig as per the terms and conditions. If you use LigDig in the course of generating work for publication you should cite the following article (and the related tools for the project that you used).
LigDig: a web server for querying ligand-protein interactions. Jonathan C Fuller, Michael Martinez, Stefan Henrich, Antonia Stank, Stefan Richter, Rebecca C Wade (2014) Bioinformatics (Oxford, England) p. 2-3
Journal link: Bioinformatics Journal
Virtual Liver: SEEK