LEWIŃSKI, T.; OTHMAN, A.M. On attainability of Hashin-Shtrikman bounds by iterative hexagonal layering. Plane elasticity problems. Archives of Mechanics, Warsaw, Poland, v. 49, n. 3, p. 513–523, 1997. Disponível em: https://am.ippt.pan.pl/index.php/am/article/view/v49p513. Acesso em: 8 jan. 2026.