Registration of scientific primary data, to make these data citable as a unique piece of work and not only a part of a publication, has always been an important issue. In the context of the project Publication and Citation of Scientific Primary Data funded by the German Research Foundation (DFG) the German National Library of Science and Technology (TIB) has become the first registration agency worldwide for scientific primary data. Registration has started for the field of earth science, but will be widened for other subjects in the future. This paper shall give an overview about the technical realization of this important usage field for a digital library.