@nprofile1q...
Do you have the DOIs of the articles? These are supposed to be stable references. If there's a DOI, you can assume that the article still exists and if there isn't one, you're probably not dealing with a publisher blocking your requests.
Do you have the DOIs of the articles? These are supposed to be stable references. If there's a DOI, you can assume that the article still exists and if there isn't one, you're probably not dealing with a publisher blocking your requests.