You could try any of the bigger dictionaries of philosophy. But the best (indeed infallible) way would
be to go to your uni library and check the catalogue. When you've found the reference, go to the
shelves where his works are kept, and I would say that you stand a very good chance that secondary
literature will right there as well. Finally, look up the topic index for 'positivism', because some of that
secondary literature might be shelved among books dealing with this particular subdiscipline, of which
Comte is indeed considered the founder.