Sums of squares, cubes, and higher powers. Jagy, William C.; Kaplansky, Irving — 1995 Experimental Mathematics
Fröhlich's local quadratic forms. Irving Kaplansky — 1969 Journal für die reine und angewandte Mathematik
Ternary positive quadratic forms that represent all odd positive integers Irving Kaplansky — 1995 Acta Arithmetica