Discrediting the source of your argument is not an ad hominem attack unless you are the person that wrote the source. Sources are not value neutral and treating them as such is not sound. Demonstrating that you have not read the studies you claim support your argument is also not an ad hominem since your argument is based on claims you are making about the studies you have not verified. Notably we are also not in a high school speech and debate class where you can just scream ad hominem over and over to win an argument.