The first volume of the Proceedings of the National Academy of Sciences was printed in 1875; to date 14 volumes have been published.
The material included in these series correspond to studies that, due to their importance, depth, originality and extension, require the aid of high-quality illustrations and maps, whose printing cost is very expensive. Because of this and the lack of resources, in the past, the publication of some volumes was left in suspense, in spite that the publication of the same had been authorized in a timely manner. For this reason, the regularity of this series was affected.