The possible Jordan forms of completions of a matrix prescribed in its upper triangular part are studied. It is shown that there always exists a nonderogatory completion for such a matrix. Jordan forms of nilpotent completions are considered as well. © 1992.
Rodman, L., & Shalom, T. (1992). Jordan forms of completions of partial upper triangular matrices. Linear Algebra and Its Applications, 168(C), 221–249. https://doi.org/10.1016/0024-3795(92)90295-L