Lewiński, T., and A.M. Othman. “On Attainability of Hashin-Shtrikman Bounds by Iterative Hexagonal Layering. Plane Elasticity Problems”. Archives of Mechanics 49, no. 3 (January 1, 1997): 513–523. Accessed January 17, 2026. http://am.ippt.gov.pl/index.php/am/article/view/v49p513.