Spira, Y., R. Lackner, Ch. Pichler, and H.A. Mang. 2005. “Viscoplastic Material Models for Soil: New Insight into the Soil-Support Interaction in NATM Tunnel Excavations”. Archives of Mechanics 57 (2-3): 209-40. http://am.ippt.gov.pl/index.php/am/article/view/v57p209.