Ballico, E. (Edoardo) , 1955-. “The Subbundles of Decomposable Vector Bundles over an Elliptic Curve”. Collectanea Mathematica, vol. 49, no. 2, Jan. 1998, pp. 185-9, https://raco.cat/index.php/CollectaneaMathematica/article/view/56450.