SudocAD is a system concerning the author linkage problem in a bibliographic database context. Having a bibliographic database E and a (new) bibliographic notice d, r being an identifier of an author in E and r' being an identifier of an author in d: is that r and r' refer to the same author ? The system, which is a prototype, has been evaluated in a real situation. Compared to results given by expert librarians, the results of SudocAD are interesting enough to plan a transformation of the prototype into a production system. SudocAD is based on a method combining numerical and knowledge based techniques. This method is abstractly defined and even though SudocAD is devoted to the author linkage problem the method could be adapted for other kinds of linkage problems especially in the semantic web context.