A good search includes the following:

A well-defined question
Keywords
A planned research strategy
Multiple sources / databases
Documentation of the search
Critique of the credibility of the source

The Dewey Decimal Classification system (DDC) is the world’s most widely used library classification system. It was created by Melvil Dewey in 1876 with aims to “organize all knowledge.” It is currently used by public libraries and smaller academic libraries throughout the world as a method for organizing books that ensures books on the same subject are near each other on the shelves. DDC assigns each book a number based on its subject matter. Subjects fall into 10 main classes, 100 divisions and 1000 sections creating a three-digit number that can be expanded with an unlimited number of decimal places to capture additional details about the item.

The Library of Congress Classification (LCC) is the system of classification used in most research and university libraries. LCC was created in 1891 specifically to meet the needs of the Library of Congress collection. It is based on twenty-one classes designated by a single letter. These are divided into sub-classes that add one or two letters to the initial class. Topics within the sub-classes are assigned whole numbers which can be expanded into decimals to identify more specific areas of the topic. This is followed by an alphanumeric author identifier which may be followed by publishing date and other details to produce a unique call number for the item. As with DDC, depending on the level of specificity needed, the call numbers can get fairly long.