Modern science is a social activity where the individualistic work of a single person doesn't exist. The advances and discoveries are made by the work of groups of investigators. An individual investigator can't exist, an isolated scientific document can either exist. If this type of documents is not more than the presentation in a support of the findings and discoveries that the authors have made, it is logical that these make reference explicit to which have been their datum points, their collaborators, the works that have preceded to him, etc. These mentions are carried out through the appointments and the bibliographic references. Each document speaks to us of other documents formed therefore the large network that is scientific literature.