As part of teaching relative clauses, getting good examples of a structure such as one of which, many of which, some of whom, i.e. quantifier/determiner + preposition + relative pronoun had always been a bit tricky. Recently I used COCA to help me find some useful sentences.
The appropriate search term is [mc*]|[d*] of which|whom|whose|who.
[mc*] is the tag for singular cardinal number
[d*] is the tag for determiners
| is the syntax for OR operator
Click on above image to see results.
The results show that all of which, many of whom, and some of which are the top three.
Some of the interesting examples in the academic register are:
1. This study suggests several directions for further work ,someofwhich we have already begun to investigate.
2. Bottlenecks at the Internet s edge can easily move between the wireless access (when its bandwidth is low) and the provider s uplink,bothofwhich can have highly variable bandwidths.
3. In its next generation of development, the Internet could make its way onto a wider range of instruments ,allofwhich will offer viewers far sharper images, a much quicker connection, and a more reliable service than at present.
There are plenty of other avenues to explore here but that would not be a quick cup of COCA :).