Can someone point out where to find up to date market/microstruture research in the options market?
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The most common online research sites are the following:
They are really good websites, since they allow to customize the research by sorting for relevance, date (that's practically what you need for), ...
I suggest you to visit some academic journals as, for instance, the Journal of quantitave finance or others like that (you can find the list just googling on the internet "finance academic journal list".
As regards this quant.SE, look at this question; different users provided a list of books in which you could find something of interest.
Lastly, I suggest you to visit arXiv.org that, IMHO, is one of the best sources for quantitative finance & market microstructure.