Reference: 
p. 54
Citation Text: 

[Chain indexing includes] each step of the hierarchical chain from the most specific to the most general. Thus, an item represented by the class number AbCfHYqZh would generate the following index entries: Nineteenth century, Germany, Manufacture, Woolen goods, Clothing (AbCfHYqZh); Germany, Manufacture, Woolen goods, Clothing (AbCfHYq); Manufacture, Woolen goods, Clothing (AbCfH); Woolen goods, Clothing (AbCf); Clothing (Ab).

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