The old textbooks had not been revised since the 1934.

The study said that more than half the science textbooks used in the elementary schools have been revised since their purchase.

It has been revised from time to time since the middle of the 20th century.

The first version of the act was effective March 31, 1961 and it has been revised since that date.

The orthography has been revised a number of times since 1968, with the most recent review in 1990.

But the watershed regulations have not been revised since 1953.

The board had revised only one budget request since 1979.

The 20-year-old act has not been revised since 1977.

The system has been revised a number of times since its establishment.

Although it is complete, it has not been revised since the 1980s.