1. Epik 1.5 (2007) Schrödinger, LLC, New York, NY
2. Perrin DD, Dempsy B, Sergeant EP (1981) pKa prediction for organic acids and bases. Chapman and Hall, London
3. LigPrep 2.1 (2007) Schrödinger, LLC, New York, NY
4. Resonance structures and mesomers are synonyms as discussed on the webpage: http://en.wikipedia.org/wiki/Resonance_structures . In the context of Epik we prefer to use mesomer because of its connection with the terminology “mesomeric effect” which often arises in discussions of pK a values
5. ACD: http://www.acdlabs.com/products/phys_chem_lab/