“…Various types of theta functions can be regarded as specializations of the symplectic theta function ϑ(τ ) = θ 1, 0 (τ, 0) (i.e., l = 1) as first observed by Eichler [7], and then also by many others (see for example [1], [2], [15], [10], and [13]). This yields an elegant way to prove transformation laws for such theta functions.…”