Dear Hiqmet Kamberaj If I understand your question correctly then I think that you mean that you cannot assign a RG DOI to publications you named 'article'. See https://help.researchgate.net/hc/en-us/articles/14293044585745-ResearchGate-DOIs for the reason why.

What you can do, when a journal has not assigned a DOI to your paper, is to create a DOI by Zenodo https://zenodo.org (if I recall correctly simply register and you can use this service). Once you have such a Zenodo DOI you can add this info here on RG for the articles it concerns.

Best regards.

Dear Rob,

thank you very much for your answer and advice.

Hiqmet