Some euclidean properties for real quadratic fields Daniel Shapiro; Raj Markanda; Ezra Brown — 1986 Acta Arithmetica
Hasse principle for the Hurwitz problem. Daniel B. Shapiro — 1978 Journal für die reine und angewandte Mathematik
On Multiples of Round and Pister Forms. Adrian Wadsworth; Daniel B. Shapiro — 1977 Mathematische Zeitschrift