Eight Black Bob books were published at infrequent intervals in 1950, 1951, 1953, 1955, 1957, 1959, 1961 and 1965.

His nephew had come there at very infrequent intervals and had never stayed for more than a day or two.

Dutch police changed their wave-lengths at infrequent intervals and had done so again only that day.

Because we'd worked over that seam of conversation at infrequent intervals, in exactly the same order.

At infrequent intervals individuals or small groups were captured and executed.

They were held at specified, infrequent intervals, though special meetings could be called if necessary.

This section was country-like, with very few houses and those placed at rather infrequent intervals.

Thus, it leaves open the possibility that happens an infinite number of times, although at infrequent intervals.

Modesitt also quotes several fictional documents at infrequent intervals throughout the book.

The signals sent by the transmitter had come at infrequent intervals, on the average of one per hour.