The question of the relationships between a word, or a text, or a symbol, and the object or concept, or idea to which it refers is a fundamental problem in many domains: philosophy, linguistics, psychology, etc. This reference problem has been tackled in many domains of Computer Science, especially in databases integration (e.g., entity resolution, record linkage, duplicates elimination, reference reconciliation) and computational linguistics (e.g., disambiguation, referring expressions). Most approaches are statistical, e.g., the object identification problem is viewed as a classification problem, but recent works, as ours, use AI techniques. We propose in this talk a simple logical framework for studying the relationships between a surrogate (a symbol in a computer system) and an entity to which it refers in an application domain. The two worlds linked by such a reference relation are irreconcilable ("La rèalitè est impossible" said Jacques Lacan), thus there is no hope to automatically solved reference problems. Nevertheless, if knowledge are used, it can be possible to help users faced with reference problems. In the proposed framework, which is motivated by actual problems in bibliographical databases, knowledge are described in terms of first order logic or in terms of conceptual graphs.