VW - CVM 1.1

p3m1 versus p31m

These two types are notoriously difficult to tell apart. An error that switched them in an early publication [reference] caused even more confusion. An excellent article by Doris Schattschneider in the American Mathematical Monthly [Sch] clarified the picture.

Test your ability to distinguish the types by classifying these four images:

p31m' versus p3m' The Algebra of Wallpapers Telling the Types Apart Negating Isometries