AOL has Bing in the footer, Yahoo had Bing references in the source view when I checked, although it looks like what tallanvor said and they just return mix of search engines.
They used to. That changed like 8 years ago. https://en.wikipedia.org/wiki/Yahoo!_Search
> AOL & Yahoo is really Bing What? I don't get that -- I don't know about AOL, but I thought that Yahoo does its own crawling (their Slurp bot)