The Creighton Moel FertilityCare System (Creighton Model, FertilityCare, CrMS) is a form of natural family planning which involves identifying the fertile period during a woman's menstrual cycle. The Creighton Model was developed by Thomas Hilgers, the founder and director of the Pope Paul VI Institute. Hilgers describes the Creighton Model as being based on "a standardized modification of the Billings ovulation method", which was developed by John and Evelyn Billings in the 1960s. The Billingses issued a paper refuting the claim that the CrMS represents a standardization of the BOM.