Dear Lou Vincent Suarez ,

unfortunately messaging via RG is only able if the addressee is following you; but in general this is not the case.

Alternatively

a) you may have a look at the publications of the authors; often there is a correspondence address available.

b) you may go the internet page of the institution of the authors(s); often the E-mails of the institution member are hidden there...

Good luck and

best regards

G.M.