The work has been done at four-year intervals so that no single Presidential couple would have to put up with the inconvenience.

Since 1958, races had been held at three- or four-year intervals, in yachts conforming to the 12-meter-class requirements.

For the next twenty years, Championships occurred at four-year intervals, although the Kapfenberg event was delayed by a year.

After 1990 the World Congresses were moved to a four-year interval.

He was reappointed at successive four-year intervals until retiring on January 31, 2006 after the second-longest tenure in the position.

They used a well-validated questionnaire to measure symptoms of depression each year, and tested all participants at two- to four-year intervals for blood sugar.

A further eight festivals were held at approximately four-year intervals until 1982.

You say that three- to four-year intervals between cup matches are "traditional."

Since the first tournament, six others have been held at four-year intervals.

She compared the women and their cognitive test results at four-year intervals, in 2003 and 2007.