If your library has bought resources on these topics, here's some advice:

• 363.7382 (Oil as an environmental pollutant) is where interdisciplinary works on oil spills are classed.
• 628.16833 (Oil spills) is where resources on water pollution engineering aspects of dealing with oil spills are classed.
• A work on the spill in San Francisco Bay might be classed in 363.7382097946 (Oil as an environmental pollutant in the San Francisco Bay Area — built from 363.7382) as an interdisciplinary work on a specific marine oil spill near land that discusses the impact on the water, and the coast is classed with the area number for the land affected.
• On the economic front, works on the foreign exchange rate of the U.S. dollar and the yen are classed in 332.4560952073 (Exchange rates of Japanese and United States currencies), while resources on the foreign exchange rate of the U.S. dollar with respect to multiple currencies are classed in 332.4560973 (Exchange rate of United States currency).
• The discovery of an almost 18 inch-long fossilized claw from the pterygotid eurypterid (a Paleozoic era "sea scorpion") made the science news recently (see the Royal Society Publishing's "Biology Letters.") Works about pterygotid eurypterid (the one from which the fossilized claw came was probably 8 feet long) are classed in 565.493 (Eurypterida).

Visit 025.431 for specific instructions on these class numbers and more. The blog is edited by Jonathan Furner, assistant editor of the DDC, with contributions from other members of the Dewey editorial team, at the Decimal Classification Division of the Library of Congress.

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