1. H. W. Alt,A free boundary problem associated with the flow of ground water. Archive for Rational Mechanics and Analysis (64),2 (1977), pp. 116–126.
2. H. W. Alt,Strömungen durch inhomogene porose Medien mit freien Rand, J. Reine Angew. Math.,305 (1979), pp. 89–115.
3. C. Baiocchi,Su un problema di frontieralibera connesso a questioni di idraulica, Ann. Mat. Pura e Appl.,92 (1972), pp. 107–127.
4. C.Baiocchi,Free boundary problems in the theory of fluid flow through porous media. Proceedings of the I.C.M. of Vancouver (1974).
5. C.Baiocchi - V.Comincioli - E.Magenes - G. A.Pozzi,Free boundary problems in the theory of fluid flow through porous media Ann. Mat. Pura e Appl. (4),97 (1973).