1- Library catalogs:
Books, magazines, etc. in the library. These are indexes of collections of printed sources organized according to certain systems. When doing topic research, it is useful to follow a transition order from general to specific. In other words, by narrowing down the subject, the exact desired area can be reached.
2- Printed Article Indexes:
Apart from book catalogues, another important resource that researchers can refer to is article indexes. These are resources that regularly cover articles published periodically, and sometimes chapters in books, according to their subjects. Article indexes, traditionally arranged in printed form, have been transferred to electronic media with the developments in computer technology and prepared in CD-ROM format and made available to readers in libraries.
3- Printed bibliography books:
Bibliographies are printed sources containing lists of published books, they can be general or specific depending on their subject. There are also bibliographies prepared for commercial purposes. These can also be useful in determining what books are available on the subject. For example: Books in print(New york: Bowker) However, such bibliographies are also published on the Internet. 
Nowadays, with the developments in internet technology, online resources have begun to replace books. This is especially due to the search feature found in large indexes and the extensive information archive that cannot be found in a library. Before starting the research, it is necessary to scan the online journals and index sites related to the subject in detail.
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