The paper deals with the problem of finding a curve, going through the interior of the domain $\Omega$, accross which the flux $\partial u/\partial n$, where $u$ is the solution of a mixed elliptic boundary value problem solved in $\Omega$, attains its maximum.
@article{104400, author = {Jaroslav Haslinger and V\'aclav Hor\'ak}, title = {On identification of critical curves}, journal = {Applications of Mathematics}, volume = {35}, year = {1990}, pages = {169-177}, zbl = {0721.49005}, mrnumber = {1052737}, language = {en}, url = {http://dml.mathdoc.fr/item/104400} }
Haslinger, Jaroslav; Horák, Václav. On identification of critical curves. Applications of Mathematics, Tome 35 (1990) pp. 169-177. http://gdmltest.u-ga.fr/item/104400/
Les méthodes directes en théorie des equations elliptiques, Academia, Praha, 1967. (1967) | MR 0227584
Finite Element Approximation for Optimal Shape Design: Theory and Applications, John Wiley & Sons, 1988. (1988) | MR 0982710