Nirmala Devi, S., and K. Mohanan. 2010. “Manganese(II), Iron(II), Cobalt(II), Nickel(II) and Zinc(II) Complexes of 2-(N-Salicylideneamino)-3-Carboxyethyl-4,5,6,7-Tetrahydrobenzothiophene ”. Asian Journal of Chemistry 14 (3):1678-82. https://asianpubs.org/index.php/ajchem/article/view/22474.