Would somebody please help me with my sentences?
Only references available from the Medline were traced, reviewed and classified and not all the advertisements were evaluated by the same investigators have threatened the validity of the results.
The use of advertisements published only in Finnish medical journals has limited the generalization of this study. On top of that, the study results exposed to the investigators bias because the researchers were involved in a program which has a conflict of interest with the results of the study.
have threatened- which threatens the validity
exposed to the investigators bias- exposed the investigators' bias (or, depending on the meaning, were exposed to...)