"Problems about technique and methods in a fifteenth-century printing house (Nicolaus Ketelaer and Gherardus de Leempt, Utrecht, 1473-1475)" by Lotte Hellinga. With an appendix on paper by Wytze Hellinga. 1976.
"Three Lions and the Cross of Lorraine" by 'Howell Heaney, Lotte Hellinga and Richard Hills. Photocopy of a book on the Barholomaeus, the English book printed on paper made in England by John Tate. Bird & Bull Press, Newtown, PA. 1992.