In this paper, we adopt a unified approach based on the concept of value set to analyze the robust strict positive real (SPR) property of uncertain systems with interval, affine linear or multilinear uncertainty structures.
Cheng, Chih-Yung and Chang, Chao-Fong
"A Unified Approach for The Robust SPR Property of a Parametric Uncertainty System,"
Journal of Marine Science and Technology: Vol. 6:
1, Article 7.
Available at: https://jmstt.ntou.edu.tw/journal/vol6/iss1/7