HENDRIK F. HAMEKA is Professor of Theoretical Chemistry in the Department of Chemistry at the University of Pennsylvania. Originally trained as a theoretical physicist, he studied quantum mechanics under H. A. Kramers (who in turn had studied under Niels Bohr). This study sparked his interest in chemical applications of quantum mechanics, which subsequently became his principal research specialty. He has written four previous textbooks on this subject, the last of which was published by Wiley.