Alphonse Willems, the first of several distinguished cataloguers of the great House of Elzevier and their Dutch printing contemporaries, identifies the father-and-son firm of Severin and Adrian Mathys as operating two presses at Nonnensteeg, Leyden, circa 1646 to 1674 (Willems 422, 424). Mathys was one of several firms which produced imitation Elzevier books.