With availability of many I & A services, the selection of suitable ones for a specific enquiry on hand would be the preliminary step. There are tools essentials. Few examples are:
i) US National Federation of Abstracting and Indexing Services: A World Guide to Abstracting and Indexing Services. Washington : NFAIS, 1963.
ii) International Federation for Documentation: Abstracting Services, Vol. 1, Science, Technology, Medicine and agriculture vol. 2Social science Humanities. The Hague, 1969.
iii) Ulrich 's International Periodicals Directory: (Carries a list of abstracting and indexing services in addition to other primary reference sources).