- Basic Collection: Provides an introductory overview. Includes basic reference materials, such as dictionaries, encyclopedias, selected editions of important works, historical surveys, bibliographies, handbooks and a few major periodicals. Librarians acquire best sellers, other popular materials and a few current, general works on a subject. The collection is weeded continually based on use.
- Support Collection: Provides all of Level 1 plus general coverage and understanding of a subject. Encompasses a wide range of representative works including some advanced titles per topic. Librarians acquire reference works, bibliographies and secondary works relating to the particular subject. The collection is weeded based on significance of title and changing use.
- Resource Collection: Provides all of Level 2 plus broad, current, in-depth and retrospective coverage to meet an extensive range of use by public library patrons. Includes the available substantive works on the subject with an emphasis on currency. Librarians acquire all important reference works, a wide selection of specialized books and an extensive collection of journals. The collection is weeded based on significance of title, usage, and maintenance of existing collection strengths.
- Comprehensive Collection: Provides all of Level 3 and encompasses the full range of use for public library patrons, from introductory works for acquiring general knowledge to primary resources for conducting historical research. Librarians acquire all significant and available current and retrospective works for comprehensive coverage of a defined and limited field. All titles and holdings are retained in a non-circulating collection with an emphasis on preservation. Weeding rarely occurs.
Expressed as a Chart
|Current and popular||collect||collect||collect||collect|
|Classics and significant titles||collect||collect||collect|
|Retrospective materials if ongoing demand||collect||collect||collect|
|Retrospective materials for resource level||collect||collect|
|Comprehensive purchasing and retention||collect|