Isoln from petroleum from Moravia province in Czechoslovakia: Landa, Machacek, Collect. Czech. Chem. Commun. 3, 1 (1933); from American petroleum: Mair et al., Anal. Chem. 31, 2082 (1959). Synthesis: Prelog, Seiwerth, Ber. 74, 1769 (1941); Stetter et al., Ber. 89, 1922 (1956); by aluminum chloride-catalyzed isomerization of tetrahydrodicyclopentadiene: Yan, Shreh, Bull. Inst. Chem. Acad. Sinica Dec. 1965, no. 11, pp 79-81. Two step synthesis starting with dicyclopentadiene: Schleyer, J. Am. Chem. Soc. 79, 3292 (1957); Schleyer, Donaldson, ibid. 82, 4645 (1960); Ludwig US 2937211 (1960 to du Pont). Reviews: Stetter, Angew. Chem. 66, 217 (1954); Fort, Schleyer, Chem. Rev. 64, 277 (1964).