THE PUBLISHERS EITHER have sought or are grateful to
the following for Permission to reproduce illustration material.
Figs4. 6 and 4.9 from D.A.Klarner(ed.),The mathe-matical Gardner(Wadsworth International,1981).
Fig. 4.7from B.Grünbaumand G.C.She Phard, Tilings and Patterns(W.H.Freeman,1987).Co Pyright?1987by W.H.Freeman and Com Pany.Usedby Permis-sion.
Fig. 4.10from K.Chand rasekharan, Hermann Weyl1885~1985(SPringer,1986).
Figs. 4.11and10.3from Penta Plexity:a class of non-Period-ictilings of the Plane.The Mathematical Intelligencer,2,32~37(SPringer,1979).
Fig. 4.12from H.S.M.Coxeter, M.Emmer, R.Pen-rose, and M.L.Teuber(eds),M.C.Escher:Artand science(North-Holland,1986).
Fig. 5.2?1989 M.C.Escher Heirs/Cordon Art-Baarn-Holland.
Fig. 10.4from Journalof Materials Research,2,1~4(Materials Research Society,1987).
All other figures(including4. 10and4.12)by the author.