Real functions with algebraic addition theorems
Joseph Fels Ritt · Transactions of the American Mathematical Society · 1927
H. A. Schwarz zu seinem fünfzigjährigen Doctorjubiläum gewidmet, p. 192.% This follows from the fact that to given values of sin x and sin y, there correspond four values of sin(*+y).361 * The quantities «, d¡, di depend on i, j, k.