1.   While death certificates are a convenient source of epidemiological data, their validity for the study of the dementing diseases is questionable.

2.   And a convenient source of water is a leaking sewer pipe.

3.   In return, Columbia hopes to get far more than a convenient source of serious books unavailable elsewhere in the city.

4.   Others also see the airlines as a convenient source of new government revenue.

5.   Probably the most convenient source of real estate income for most investors is a real estate investment trust, investment advisers say.

6.   Suddenly, the Web is the most convenient source for information.