Williams, M. (1991) “THE CREATION OF WEAK SIGULARITIES IN REFLECTING SEMILINEAR WAVES”, Ann. Sofia Univ. Fac. Math. and Inf, 82(1), pp. 53–61. Available at: https://ftl5.uni-sofia.bg./index.php/fmi/article/view/522 (Accessed: 24 November 2024).