In the Library, call numbers are the "addresses" of books on the shelves. In political science and international relations, the call numbers start with the letter J, according to the Library of Congress classification system, and here are the basic interpretations:
J = general legislative or executive papers
JA = general political science
JC = political theory and philosophy of the state
JF = governments generally, political institutions or public administration
JK = government, political institutions or public administration of the United States
JL = government, political institutions or public administration of Western Hemisphere
JN = government, political institutions or public administration of Europe
JQ = government, political institutions or public administration of Asia, Africa, Australia/New Zealand, Middle East, Pacific Area
JS = city, county or regional local government or public administration
JV = colonies, colonialism, human migration
JX = (obsolete) foreign relations, diplomacy (see JZ)
JZ = international relations, world politics, diplomacy, international security, international law