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Form Numbers

• At NLM, classification by publication type takes precedence over classification by subject
  • For example, an atlas of Liver Neoplasms is classed in WI 17 along with atlases on any other subject covered by the WI schedule for digestive diseases
  • Other libraries that prefer to shelve material by topic can assign a subject call number

• When both a main heading and a subheading have their own form numbers, generally classify for the subheading
  • For example, for a work with the subject Education, Nursing $x history, use WY 11

• When both a topical subheading and a publication type are classified by form, classify for the publication type
  • For example, for a work with the subject Surgery $x history and the publication type Outlines, use WO 18.2
• When more than one publication type is used, classify for the one deemed most important