Animal Planet: Adolescence and Sexual Maturity
Describes the stages of development in a cat's life from kittenhood to full sexual maturity.
Purina Cat Chow: How Often Do Cats Come into Heat?
Explains how often cats come into heat and how long the heat period is.
The Winn Feline Foundation: The Estrus Cycle of th
Explains the estrus cycle and ovulation in queens.