In 1857 Marx explained that in a letter to Engels, commenting on his predictions published in New York Times:

To the Editor: A Dec. 2 letter, commenting on the right of graduate students to unionize at universities, criticized the quality of American academic research.

Men may be from Mars and women from Venus, but this is not apparent in your choice of letters (March 12) commenting on Jack Hitt's article (Feb. 20).

In October 2009, Butterworth published an open letter commenting on the extensive litigation concerning the 33rd America's Cup.

The Labor Department received more than 75,000 e-mail messages and letters commenting on its draft proposal.

In fact, the S.E.C. has received more than 300 letters commenting on this package, which it considers an astounding number.

His collection Dear Fathers was several letters commenting on needed reforms in the Vatican.

Senator Levin's letter [PDF] commenting on the Federal Reserve's proposed amendments to Regulation Z, which implements the Truth in Lending Act - October 12, 2007.

Senator Levin's letter [PDF] commenting on the Federal Reserve's proposed strengthening of rules to prohibit unfair or deceptive acts involving credit cards - August 4, 2008.

Using a manual typewriter, Warner wrote literally tens of thousands of letters commenting on fanzines.