Try this URL: http://eclectic.ss.uci.edu/~drwhite/Austria/index.htm

This is older than the peer-reviewed study. Google "structural endogamy" or write one of the professors listed.

The "birth" dates in Achomitz/Feistritz kept at Castle Wasserleonburg go back as far as 1470 for Schnabl and 1490 for the oldest of the other numerous surnames. Possibly the only 1470 date was an error...