Use of article with equivalent (n)

[Annetteh]

I am more and more seeing "such-and-such and equivalent" (or "or equivalent") rather than "such-and-such and the equivalent." Are both usages correct, and are there any source materials that discuss either or both usages?

Thanks~

[Tdol]

According to the British National Corpus, 'and equivalent' is more common. You can search here for examples:
[DAVIES] Variation in English Words and Phrases (VIEW)
However, 'equivalent' could be used as a noun or adjective, which would have an effect on whether to use the article or not.