Integration of library data into the Semantic Web environment is a key issue for libraries and is approached on the basis of interoperability between conceptual models. Several data models exist for the representation and publication of library data in the Semantic Web and therefore inter-domain and intra-domain interoperability issues emerge as a growing number of web data are generated. Achieving interoperability for different representations of the same or related entities between the library and other cultural heritage institutions shall enhance rich bibliographic data reusability and support the development of new data-driven information services. This paper aims to investigate common ground and convergences between four conceptual models, namely Functional Requirements for Bibliographic Records (FRBR), FRBR Object-Oriented (FRBRoo), Bibliographic Framework (BIBFRAME) and Europeana Data Model (EDM), enabling semantically-richer interoperability by studying the representation of monographs, as well as of content relationships (derivative and equivalent bibliographic relationships) and of whole-part relationships between them.