X theorem or X's theorem I am always stuck by the randomness of some syntax rules in academic articles, hence I cannot infer a proper answer to this question:


  Is there a correct way to choose among "X theorem" and "X's theorem"?


I chose the word "theorem" for my concern comes from reading mathematics, but of course this questions stands for any reference to someone's work.
In health and medicine, there is a concerted effort to move away from possessive attributive eponyms. Thus, instead of Alzheimer's disease, it's now Alzheimer disease. The same is true of Parkinson disease, Gram stain, Cushing syndrome, etc.