Cf. - sustany/dvg GitHub Wiki

Cf. is an abbreviation for the Latin word�confer, meaning "compare."� Cf. is a�signal�indicating that the cited source supports a different claim (proposition) than the one just made, that it is worthwhile to compare the two claims and�assess the difference. Parenthetical explanations are encouraged to explain how a�cf.�source relates to the text.

In other words, a�cf.�source simply offers a different yet non-contradictory claim and actual support to the claim just made should not be assumed.�If the source gives a contradictory claim, a�negative signal�should be used.