Here are two articles about changes Google has made to search which affect required terms. First Google started silently ignoring some of the search terms included in multiple term searches (making all search terms required by default was one of the reasons I originally liked Google better than Yahoo). Then more recently they stopped supporting the "+" to force term inclusion, apparently because they want to use that in searches involving Google+.

Google Just Made Bing the Best Search Engine

Google Kills Its Other Plus, and How to Bring It Back

In years past, I could have searched for things like the following and only gotten pages that had all these terms:

bengals highlights simpson

I would only double-quote exact phrases I wanted matched, such as "Cat on a Hot Tin Roof"

When I noticed the first change above several months ago, I started using the + operator, which had been previously redundant:

+bengals +highlights +simpson

Now it appears we have to separately double-quote each term we require which is a pain:

"bengals" "highlights" "simpson"