1. a British Patent GB-1232201-R to Pennsalt Chemicals Corp.: (b) W. T. Flowers, R. N. Hazeldine and S. A. Majid, Tetrahedron Letters, 2503 (1967).
2. S. D. Moshchitskii, L. S. Sologub and Ya. N. Ivashechenko, Khim. Geterosikl. Soedin., 1068 (1968).
3. Chem. Abstr., 70, 777382 (1969).
4. “The Chemistry of Heterocyclic Compounds. Pyridine and its Derivatives,” Part 3, Interscience Publishers, New York, 1962, p. 81.