Periodicals and Serials:

Primary periodicals constitute one  of the most indispensable categories of publications  in academic  research and special libraries. A substantial part of the collection in these libraries are periodical literature. More than 50% of the funds are spent in the acquisition of current titles of periodicals. Subscriptions to primary and secondary  periodicals arc steadily rising and there  are hundreds and thousands of titles in several disciplines competing with each other for inclusion. It is unwise to include a title of a periodical for a few years and discontinue sub-scribing to it later. Considerable thought and attention ought to be given to decide the inclusion of a title. 

Ulrich International Periodicals Directory. Edn.27, R.R. Bowker, New York, 1988. This directory includes 71700 titles of periodicals in all subjects from 160 countries. A separate list of abstracting and indexing services is also included. The Ulrich's quarterly updates the directory with new titles, title changes and discontinuations. 

Irregular Serials and Annual,  an International Directory  which Ulrich used to publish since 1967 has now been merged with the Periodicals Directory. Hence there are additional entries of 99,450 irregular serials and annuals. 

Since 1988  Ulrich also supplies free of charge  Ulrich 's Update,  a quarterly supplement to the Periodicals Directory. This facility is extended to those who have a 1988-89 copy of Directory.

N. W. Ayer  & Son's Directory of Newspapers and Periodicals. 1880 -  Annual. Philadelphia, . Ayer. This directory lists over 22,000 newspapers and magazines primarily limited to the United States and Canada. 

Besides these type of directories, lists brought out by major abstracting and indexing services like Chemical Abstracts, Science Citation Index, the Engineering Index etc., are invaluable sources of information for selection of current titles in the respective disciplines. The lists represent international coverage, irrespective of language or place of publications. The Science Citation Index gives the most cited titles of about 4,000 scientific periodicals from among thousands that are published.