Lehninger AL, Nelson DL & Cox MM, 1993
Nelson and Cox report a nearly complete set of pK values in their first rewrite of Lehninger's classic biochemistry text book, Principles of Biochemistry (1993) (1). The pK values are for the free amino acids in solution, as that is the area in which they are introduced, and these values are applied to problems relating to the free amino acids. These pK values remain unchanged through subsequent editions of Principles of Biochemistry.
Amino acid pK values from Lehninger AL, Nelson DL & Cox MM, 1993 (1).