M. Ibrahim, M. et al. 2012. Crystal Structure and Density Functional Calculation of (E)-4-Hydroxy-3-methyl-N’- (thiophen-2-ylmethylene)-1,4-dihydroquinoxaline-2-carbohydrazide Radical. Asian Journal of Chemistry. 24, 7 (Mar. 2012), 2926–2930.