Complex sentence: Almost all the papers published before 1996 describe classic pre-Web hypertext and hypermedia; the majority of papers published since 1996 are devoted to Web-based adaptive hypermedia systems.
Split into simpler sentences: Almost all the papers published before 1996 describe classic pre-Web hypertext and hypermedia. In contrast, the majority of papers published since 1996 are devoted to Web-based adaptive hypermedia systems.