Boundary value problems with a free boundary in the theory of stationary filtration
From the text: "The problem of steady-state filtration in porous media leads to a boundary value problem with a free boundary for a linear differential equation of elliptic type. C. Baiocchi [Ann. Mat. Pura Appl. (4) 92 (1972), 107–127; MR0408443] proposed a new technique for solving such problems. Not only does this technique permit one to obtain theoretical results which are rigorous from the mathematical point of view, but it is also useful in applications. The main idea consists in reducing...