At the dawn of the digital age, the importance of the documentation of mathematical knowledge assumes a strategic and decisive character, both in current research as well as in the transmission to future generations. Of course, this is something that happens in all branches of knowledge. Documentary resources such as databases, publication archives, or electronic resources (digital books or simple web pages), as well as increasingly powerful search engines, are essential instruments not only for science but also for the economy and the information society. However, for mathematics and all who use it, the importance of documentation is strengthened by the generality and permanence intrinsic to the subject, to which is due its unique situation amid the other branches of human knowledge.