The prestige of the encyclopaedias is enhanced by some of the unique features employed in the publication of encyclopaedias.
i) Most of the major articles in the encyclopaedia are appended with the bibliography for further reading. Few encyclopaedias give bibliography in classified manner in the last volume. The current, exhaustive, updated bibliography in each subject is very useful for readers to pick up the thread and progress forward.
ii) The appendices and separate lists of measures and weights, abbreviations, errata, pronunciation etc. improve the value and are very handy to glance through information.
iii) The unique feature of the encyclopaedia is the exhaustive index giving `see' and 'see also' cross references to enable the user to locate the information quickly and easily.
iv) The comprehensibility of the encyclopaedia increases with the proper illustrations in the form of photographs, maps, sketches, diagrams, charts, tables etc., given at the appropriate places in the articles.
v) The inclusion of guidelines for using the volumes and contents of each volume in the introductory pages are the important features to render help to the information seekers.
The librarian should be guided by the above criteria for purchasing valuable sets of encyclopaedias for the reference section. There are some secondary evaluation sources and library journals which review the new additions to the
encyclopaedias. They should be properly scanned through before taking decision. There are some unscrupulous publishers who give copy right permissions to various other publishers for publishing a particular set. The same set of encyclopaedia is published by two to three publishers under various titles. They cause unnecessary duplicacy of expensive sets in the library which could be shifted by few other sets.