%0 Journal Article %A Piotr J/edrzejewicz %T On rings of constants of derivations in two variables in positive characteristic %J Colloquium Mathematicum %D 2006 %P 109-117 %V 106 %N 1 %I mathdoc %U http://geodesic.mathdoc.fr/articles/10.4064/cm106-1-9/ %R 10.4064/cm106-1-9 %G en %F 10_4064_cm106_1_9