The Rule of St. Benedict

From Easter till the calends of November let the whole psalmody, as explained above, be said, except that on account of the shortness of the nights, no lessons are read from the book; but instead of these three lessons, let one from the Old Testament be said from memory. Let a short responsory follow this, and let all the rest be performed as was said; namely, that never fewer than twelve psalms be said at the night office, exclusive of the third and the 94th psalm.