When you ask the question, “has this author been cited in other resources? ” which aspect of the web resource are you evaluating? reliability currency relevance authority

When you ask the question "Has this author been cited in other resources?" you are evaluating the relevance of the resource. You cite a source in order to get a stronger picture of its intellectual value. And if the author (the source) you cited has been cited in other resources too, this means that the source is reliable (is able to be trusted), you are evaluating the reliability of the source. 
There are several reasons why you should cite resources in your works: to proof your thesis, to show proper research and many more.

Where is the picture at