are "counter-rotating" and "contra-rotating" interchangeable terms?

I'm doing some research, trying to find information on airplanes with
counter-rotating props, but I'm getting a lot of junk hits from
articles that use "counter-rotating" when they should mean
"contra-rotating".

I was always taught that "contra-rotating" was when you had two sets of
blades spinning from the same hub, as in this: http://tinyurl.com/vxu9a
and "counter-rotating" meant two different engines on a twin, each
spinning in opposite directions, ala the Seneca and Twin Comanche.

But according to google, more than half of the instances of
"counter-rotating" are used to describe "contra-rotating". Are all
those people wrong, or is the term interchangeable?

(by the way, I'm trying to compile a list of counter-rotating twins, if
anyone knows of any that are not listed he
http://en.wikipedia.org/wiki/Counter...ing_propellers please post)