Let S be a nonempty, proper subset of all refined inertias. Then, S is called a critical set of refined inertias for ireducible sign patterns of order n if is sufficient for any sign pattern A to be refined inertially arbitrary. If no proper subset of Sis a critical set of refined inertias, then S is a minimal critical set of refined inertias for sign patterns of order n . In this paper, all minimal critical sets of refined inertias for irreducible sign patterns of order 2 are identified. As a by-product, a new approach is presented to identify all minimal critical sets of inertias for irreducible sign patterns of order 2.
 B. L. Yu, T. Z. Huang, J. Luo and H. B. Hua, “Critical Sets of Refined Inertias for Irreducible Zero-Nonzero Patterns of Orders 2 and 3,” Linear Algebra and Its Applications, Vol. 437, No. 2, 2012, pp. 490-498. doi:10.1016/j.laa.2012.03.007