A more thorough explanation:

Definition: Cf. is an abbreviation for the Latin word confer, which means "compare." It is used to signal that the cited source supports a different claim than the one just made, and that it is worthwhile to compare the two claims and assess the difference. When using cf., it is encouraged to provide parenthetical explanations to explain how the source relates to the text. It is important to note that 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.

Example 1: "The study found that eating a diet high in fruits and vegetables can reduce the risk of heart disease. Cf. another study that found no significant difference in heart disease risk between those who ate a high fruit and vegetable diet and those who did not." In this example, the use of cf. signals that there is a different claim being made in the other study, and it is worth comparing the two claims to assess the difference.

Example 2: "The author argues that the death penalty is an effective deterrent to crime. Cf. a study that found no evidence to support this claim." In this example, the use of cf. signals that there is a contradictory claim being made in the study, and a negative signal should be used to indicate that the claim is not supported.

These examples illustrate how cf. is used to signal a different claim and encourage comparison and assessment of the difference between claims. It is important to use cf. carefully and accurately to avoid assuming support for a claim that may not be present in the cited source.