Random House, New York, 1969.

Lutz, Frank E., “'Invisible’ Colors of Flowers and Butterflies,”

Natural History,

Vol. XXXIII, No. 6, November/December 1933.

Maclay, W. S. and E. Guttman, “Mescaline Hallucinations in Artists,”

Archives Neurology and

January 1941.

Matthaei, Rupprecht,

Goethe’s Color Theory,

Van Nostrand Reinhold Co., New York, 1970.

Bog aan la aqoon