@article{JRAM_1979__310_152148,
     author = {A. de Korvin and C. Roberts and R.A. Al\'o},
     title = {The optional sampling theorem for convex set valued martingales.},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {1--6},
     publisher = {mathdoc},
     volume = {310},
     year = {1979},
     zbl = {0416.60012},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1979__310_152148/}
}