<E. Fischer and F. Jourdan, Ber. 16, 2241 (1883); E. Pischer and 0. Hess, Ber. 17, 559 (1884)
G. M. Robinson and R. Robinson, J. Chem. Soc. 113, 639 (1918)
C. F. H. Allen and C. V. Wilson, J. Am. Chem. Soc. 65, 611 (1943)
H. Plieninger and I. Nogradi, Chem. Ber. 88, 1964 (1955)
R. B. Carlin, W. O. Henley, and C. P. Carlson, J. Am. Chem. Soc. 79, 5712 (1957)
R. J. Owellen et al., Tetrahedron Letters 1967, 1741
Reviews: R. B. van Orden and H. G. Lindwell, Chem. Revs. 30, 78 (1942)
P. Julian et al., Heterocyclic Compounds 3, 8, 14 (New York, 1952)
B. Robinson, Chem. Revs. 63, 373 (1963)