TY  - BOOK
AU  - Gregory,R.L.
AU  - Gombrich,E.H.
TI  - Illusion: in nature and art 
SN  - 0715607558 :
U1  - 152.73 
PY  - 1973///
CY  - London
PB  - Duckworth
KW  - Optical illusions
KW  - Visual perception
N1  - Includes index
ER  -