V. von Richter, Ber. 16, 677 (1883)
M. Busch and M. Klett, Ber. 25, 2847 (1892)
N. J. Leonard, Chem. Revs. 37, 270 (1945)
K. Schofield and J. C. E. Simpson, J. Chem. Soc. 1945, 512
K. Schofield and T. Swain, ibid. 1949, 2393
J. C. E. Simpson, Condensed Pyridazine and Pyrazille Rings, p 16 (New York, 1953)
E. H. Rodd, Chemistry of Carbon Compounds IVB, 1217 (1959)

Cf. Widman-Stoermer Synthesis.