Friedrich Haag (20 August 1856 – 8 December 1941) was a pioneering German crystallographer.Doris Schattschneider Tiling the plane with congruent pentagons, Math. Mag., 1978, Volume 51, pp. 29–44
An article written by Haag in the (a German crystallography journal) was used by M. C. Escher in his study of tessellation.Haag Die regelmäßigen Planteilungen und Punktsysteme, Zeitschrift für Kristallographie, Volume 58, 1923, pp. 478–489Doris Schattschneider The Mathematical Side of M. C. Escher, Notices AMS, June/July 2010, p. 707
References
External links :de:Friedrich Haag (Kristallograph) (on German Wikipedia)