Excuse me, some papers published in international conferences are guaranteed to be retrieved by Ei Compendex, and some are retrieved by Ei. What's the difference between them? Which authority is greater? EI？ Compendex？ Index summary? (also called core data). Including the title and abstract of the paper, indexing and deep processing with subject words and classification numbers. Whether there are subject words and classification numbers is the only sign to judge whether a paper is officially included in EI. The EI retrieval sometimes means that only the title or abstract is retrieved in the EI database, and the handling institution should ask clearly.