You may also wish to search for items by Kettler, R. and Kettler.
Only one matching reference was found.
Kettler, R.M.; Wesolowski, D.J.; Palmer, D.A., Dissociation Constants of Oxalic Acid in Aqueous Sodium Chloride and Sodium Trifluoromethanesulfonate Media to 175 C, J. Chem. Eng. Data, 1998, 43, 337-50. [all data]