The Summa Monacensis and its Relatives. In his study on the birth of the Parisian school of canon law Peter Landau argues that the Summa Parisiensis was not written in Paris, as has commonly been thought, but in Sens, and that the Summa Monacensis marks the beginning of the Parisian school of canon law. The question of precedence having remained open, the Summa Monacensis and and its relatives, the so-called circle of the Summa Monacensis, indeed are an important foundation of the Parisian school of canon law. The present study tries to elucidate the internal relations of the circle of the Summa Monacensis. More precisely, drawing on some major works of the circle, it tries to prove Stephan Kuttner's hypothesis of a common source attributed to an unknown master. It will be argued that there seems to have been a common source, of which each work of the circle represents a unique form of tradition. Following Landau's argumentation, it will also be argued that the common source should be attributed to the author of the Summa Monacensis.