Google Scholar is a useful tool for locating articles in academic journals and papers. Start from the Library database list when searching Google Scholar in order to see links to Cheng Library holdings.
Here's the Direct link to Google Scholar
Search for books on management theories in other libraries by using WorldCat - the OnlineUnion Catalog.
If the Cheng Library doesn't own the book, consider requesting an interlibrary loan.
While there are plenty of references to management theorists on the Web, most of what is there represents snapshots of theorists, their biographies and abstracts of works. Here is a brief list of the types of resources available online. Contemporary theorists may have their own webpages.