- Spectral studies of semicarbazones derived from 3- and 4-formylpyridine and 3- and 4-acetylpyridine: crystal and molecular structure of 3-formylpyridine semicarbazone. Beraldo, H., Nacif, W.F., West, D.X. Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy. (2001)