Gregory is writing a paper on robots. He thinks that robots will one day replace pets like dogs or cats. He gets some books from the library. He also decides to look through some online web pages. The books are written by a scientist from the University of Nebraska. The web pages and books have quotes that agree with Gregory's opinion. The books that Gregory uses were published in 1999. The articles from the web pages are also written by scientists. They were published in 2003.

What is one way for Gregory to decide which source is more credible

Question

Gregory is writing a paper on robots. He thinks that robots will one day replace pets like dogs or cats. He gets some books from the library. He also decides to look through some online web pages. The books are written by a scientist from the University of Nebraska. The web pages and books have quotes that agree with Gregory's opinion. The books that Gregory uses were published in 1999. The articles from the web pages are also written by scientists. They were published in 2003. 

What is one way for Gregory to decide which source is more credible