There's quite a lot to work with, but here's a sample...

"Wexler argues from linguistic and other evidence "that the Ashkenazic Jews must have consisted of a mix of Greek, Balkan Romance and Balkan Slavic, Germano-Slavic and Turkic (Khazar, Avar) converts to Judaism and their descendants and only a minority of ethnic Jews—many of whom in all probability came from other parts of Europe rather than Palestine itself." Wexler rejects the Khazar mass migration hypothesis on linguistic grounds, arguing that there was more conversion in place than migration. "Hence, contemporary Judaism is best defined not as the continuation of the Judaism which served as an antecedent of Christianity and Islam, but as a newly Judaized variant of European (mainly Slavic) paganism and Christianity…most of the features of Old Palestinian Judaism and Semitic Hebrew to be found in Ashkenazic 'Judaism' and Medieval Ashkenazic/Modern Israeli 'Hebrew' were latter borrowings rather than original inheritance [original emphasis]." This thesis has been obscured by philo-German and anti-Slavic chauvinism among scholars, Jewish and non-, of Ashkenazi Jewry, by disciplinary blinders, and by inertia."

http://theglobalrealm.com/2010/02/06/the-invention-of-the-jewish-people/

A couple of years ago, I provided a synopsis of Schlomo Sands' book on this subject and another mudcatter provided what they apparently thought was a rebuttal of Sands' main thesis, but when I read the review, its main problem with Sands' work was that he seemed to think he was breaking new ground, and they were saying that what he had published was already common knowledge among Israeli academics. I'll try to find that one.