So the I.O.M.proposed that residents be required to get five continuous hours of rest for every sixteen hours on duty.

VOA: special.2009.06.02

And for the space of four hours every night, I feel no boredom.

每晚四小时的学习，我一点也不觉得无聊。

耶鲁公开课 - 政治哲学导论课程节选

Like in high school, every day I would be in school for like six and half hours.

我在高中的时候，每天都会在学校学习六个半小时。

耶鲁的忙碌生活 - SpeakingMax英语口语达人

Make regular stops -- every two hours for a puppy, every three to four hours for a cat or an adult dog -- so your pet can take a walk on a leash (some cats enjoy a little leash walk).

CNN: Tips for road tripping with pets

Men only think about sex once every two hours - not every seven seconds, as is commonly believed, according to a survey of 5, 000 adult males.

BBC: 10 stories that could be April Fools pranks but aren't

These include prohibiting parents and visitors from touching babies with artificial nails, which can harbor bacteria, and requiring staffers to change tubing only every 72 hours instead of every day, to avoid unnecessary invasive contact with the baby.

WSJ: How Hospitals Save More Lives and Reduce Infections in Premature Babies