should be able to leave kudos on scientific studies. i liked your paper dude keep at it
sorry, Dr. Dude
Dude et. al.
need y'all to know that most academics have publicly searchable email addresses and this not only makes their day but they can put nice emails in their giant packets for applying for jobs or tenure. "hi i read your paper for a class and it was very helpful, im at xyz college and the class is blah with professor blah" is sufficient and ENORMOUSLY helpful