Convex Noncommutative Polynomials Have Degree Two or Less. - J. William Helton; Scott A. McCullough (SIAM J. Matrix Anal. Appl., 2004)

Convex Matrix Inequalities Versus Linear Matrix Inequalities. - J. William Helton; Scott A. McCullough; Mihai Putinar; Victor Vinnikov (IEEE Trans. Autom. Control., 2009)

Relaxing LMI domination matricially. - J. William Helton; Igor Klep; Scott A. McCullough (CDC, 2010)

The matricial relaxation of a linear matrix inequality. - J. William Helton; Igor Klep; Scott A. McCullough (Math. Program., 2013)

Noncommutative Polynomials Describing Convex Sets. - J. William Helton; Igor Klep; Scott A. McCullough; Jurij Volcic (Found. Comput. Math., 2021)