= Lommen, Theosophy and Lettering Klaas van Leeuwen’s Letterboek voor den teekenaar en ambachtsman, 1907 (2025), p.6-7: "In the explantory notes, Van Leeuwen sets out his principles and describes the numbered sheets individually. With this publication, he aims to 'provide letter examples for those who have to use letters in their trade, either by executing them directly or providing a drawing for them. After all, the various ways in which letters can be applied in the former - painted, carved, engraved, or cut in stone - all rely on hand lettering, which is why it has been treated exclusively in this book. As opposed to the printing letter, we could therefore speak of the drawn letter here. Van Leeuwen also took geometrical constructions as a basis in his lettering: 'To (...) obtain unity of form in analphabet in the easiest way, it is necessary to draw the letters on simple basic forms, which for our alphabet are the square and the circle. From the circle and square with its diagonals and centre lines, the core shapes of our letters are developed.' Most of the designs are presented in a series of three sheets, successively depicting the construction, a letter overview/ alphabet and a fictional application, with room for minor variations. Each sheet is surrounded by an ornamental border."In 1988 a monograph on the designer was published on occasion of a large memorial exhibition by Margriet Knol: Klaas van Leeuwen 1867-1935 (Assen: Drents Museum). Stamp on title-page and inside portfolio. (Ambachtsschool Amsterdam). Backstrip partly worn.