Huanying Bian, Yedan Shen & Guanghui Hu. (1970). An $h$-Adaptive Finite Element Solution of the Relaxation Non-Equilibrium Model for Gravity-Driven Fingers.
Advances in Applied Mathematics and Mechanics. 13 (6).
1418-1440.
doi:10.4208/aamm.OA-2020-0218