1. see " Mechanistic Organic Photochemistry Ed Reynold Pubi Corp New York for a more comprehensive review on photocyclization see Stermitz in " Organic Photochemistry Vol Marcel New York ehem org Chemistry a Comm org Chemis - try Adel and physik;Neckebs;Soc chem Soc chem Soc Chem,1967
2. trans form does not photocyclize directly but only after some eis isomer is produced , as found by Stegembybr for stilbene;Stegemeyek;Naturforsch b,1962
3. II ehem;Hammond;Soc chem Soc,1962
4. Chem Neue Folge a Ibid;Bobtolus;Tetrahedron Letters chim ital,1966