Be courteous and thankful. Many works of fiction are available online , but only those not restricted by copyright. There aren't very many Internet resources which have the depth and breadth of a good book. Try the library. However, you might find discussions or shorter length pieces relevant to your topic on the Internet to supplement a good book.
Many web sites are similar in depth and scope to magazine articles.
Try a keyword search with terms you might find in a pamphlet about your topic. You might save a lot of time by just consulting the reference book directly or asking a reference librarian. If those aren't available options, there may be an online version of the reference book you have in mind. Many government documents are available online , many are not. Be sure to consult with a librarian if you don't find what you need.