Donald E. Knuth, Knuth meets NTG members, NTG: MAPS. 16 (1996), 38–49. Reprinted as Questions and Answers, III, chapter 33 of Digital Typography. str. 648.
Donald E. Knuth. Typesetting Concrete Mathematics, TUGboat 10 (1989). str. 31–36. str. 342. Reprinted as chapter 18 of Digital Typography. str. 367–378.