1. Aqueous pKa compilation by Williams R (document compiled by Jencks WP, added to by Westheimer FH). http://research.chem.psu.edu/brpgroup/pKa_compilation.pdf . Accessed 11 Mar 2014
2. Aqueous pKa compilation with some dimethyl sulfoxide values by Ripin DH, Evans DA. http://www2.lsdiv.harvard.edu/labs/evans/pdf/evans_pKa_table.pdf . Accessed 11 Mar 2014
3. pKa values in dimethyl sulfoxide compilation by Bordwell FG. http://www.chem.wisc.edu/areas/reich/pkatable/index.htm . Accessed 12 Mar 2014
4. Links to tables of pKa values in non-aqueous solvents taken from literature by Leito I. http://tera.chem.ut.ee/~ivo/HA_UT/ Accessed 12 Mar 2014
5. Albert A (1963) Ionization constants of heterocyclic substances. In: Katritzky AR (ed) Physical methods in heterocyclic chemistry. Academic Press, New York