S. Nirmala Devi and K. Mohanan, “Manganese(II), Iron(II), Cobalt(II), Nickel(II) and Zinc(II) Complexes of 2-(N-Salicylideneamino)-3-Carboxyethyl-4,5,6,7-Tetrahydrobenzothiophene ”, ajc, vol. 14, no. 3, pp. 1678–1682, Mar. 2010.