Musannaf Ibn Abi Shaybah

Hazrat Harith (may Allah be pleased with him) says that a woman will be considered to have istihada (non-menstrual bleeding) when her menstruation exceeds the maximum limit after which women become pure.

Hazrat Hakam (may Allah have mercy on him) says that when one menstruation reaches the next menstruation, the woman is mustahadah (experiencing abnormal bleeding).