Wallace G. Walker spent most of his career as an independent artist residing in New York City. He was a graduate of Cranbrook Academy of Art, Bloomfield Hills, Michigan and the inventor of IsoAxis (R). He worked for I.M. Pei and Partners and taught at both Parsons School of Design and the New York Institute of Technology. He had numerous shows and exhibits in cities across the USA. He returned to his hometown of Shreveport, Louisiana in 1989 and continued his artistic activities until his death in 2003. Doris Schattschneider is Professor Emerita of Mathematics at Moravian College in Bethlehem, Pennsylvania, where she taught for 34 years. Her dual interest in geometry and art led naturally to the study of M.C. Escher's work. Active as a teacher, lecturer, editor, and writer, she has published widely on Escher's work. Her book, M.C. Escher: Visions of Symmetry (Abrams, 2004) gives a complete account of Escher's symmetry work, and includes color photographs of all 150 of Escher's symmetry drawings.