On pages 338 and 339 in his first notebook, Ramanujan records eighteen
values for a certain product of theta-functions depending on two inte
gral parameters m and n. When (m, n) = 1, it can be seen that each of
these values is a unit. The purpose of this paper is to establish each
of these eighteen values and to prove that under certain general cond
itions this product is indeed a unit. Lastly, we prove that certain qu
otients of theta-functions are algebraic integers.