I wish to describe a theorem of somebody X and also the statement of the theorem, and my first attempt is something like a theorem of X that gives a lower bound of ... . Then I immediately realized that such description will induce some confusion about the antecedent of that. At length I reached the formulation a theorem that belongs to X and that gives a lower bound of .... It is, however, sounds no idiomatic and annoying. So I wish to know the optimal way to present what I wish to present.
Moreover, is there any general rule guiding the usage for relative pronouns with possible multi-antecedent?
Thanks so much.