Almost half — or 46 per cent — cleaned their keyboard less than once a month.

近半数的人(46%)一个月内不会清洗一次键盘。

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Price list on their Web site is updated infrequently (less than once a month).

在其网站上的 价目表不常更新（每月少于一次）。

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Those using cell phones less than once a month increased the odds of being very tired one year later by 1.8.

每月(熄灯后)使用手机小于一次，就会使一年后非常疲劳的机率增加1.8%。

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People who ate these types of fish one to four times per week had a 28% lower risk of AF compared with those who ate fish less than once a month.

BBC: NEWS | Health | Fish prevents deadly heart rhythms

The price of things that you might buy every day such as bread or milk is more important than something you might buy less than once a month such as a haircut.

BBC: Inflation calculator: How does it work?

And women who had migraines with auras less than once a month (75 percent of the group) were more than twice as likely as migraine-free women to have a heart attack, and almost twice as likely to have had a heart procedure, such as bypass surgery.

CNN: Women's migraines linked to higher stroke, heart attack risk