As SLSH is not backed by any library collection, so updating and revision of subject headings cannot keep pace with changing current terminology and growth of new subjects. While revisions are taken care of by publishing new editions of SLSH at periodic intervals, tools that can help libraries to keep the subject headings current and updated are the "Readers' Guide to Periodical Literature", "Applied Science and Technology Index", etc. which are also published by Wilson Company. These bibliographic tools provide acceptable current subject headings, using the principles of LCSH and SLSH. If these headings also are found inadequate, the subject cataloguer is advised to construct the headings on the basis of the principles of subject headings of SLSH.