Long before the invention of the internet, scientists had found ways to communicate their results to their colleagues before the peer review and publication process of professional journals had become completed: They sent pre-prints to important institutions and selected colleagues. Depending on the technical capabilities, these might be papers typed by hand, and with hand-written formulae. Institutes came to assign systematic "preprint numbers", which allowed scientists to quote a preprint even before the article itself had appeared in print (in the image, on the left you can see a preprint with numbers assigned by the European nuclear research centre CERN and the University of California at Los Angeles, UCLA).