Schwartz, C.W., Einstein, H.H., and Salazar, G.F. (1992). Instructional modules for tunnel design and construction. In Computing in Civil Engineering and Geographic Information Systems Symposium: Proceedings of the 8^th National Conference (B.J. Goodno, J.R. Wright, eds.), 7-9 June, Dallas, Texas, pp. 368-375. Published by the American Society of Civil Engineers, 1992. ISBN 978-0872628694