 Several important classes are given here.In the table below, "P"("x"), "Q"("x"), "P"("y"), "Q"("y"), and "M"("x","y"), "N"("x","y") are any integrable functions of "x", "y", and "b" and "c" are real given constants, and "C"1, "C"2... are arbitrary constants (complex in general).The differential equations are in their equivalent and alternative forms that lead to the solution through integration.