Columbia subject headings:
Espionage--Canada--History--20th century.
Sawula, Emma, 1921?-1974.
Spies--Canada--Biography.
Harvard subject headings:
Espionage--Canada--History--20th century.
Sawula, Emma, 1921?-1974.
Spies--Canada--Biography.
Women spies--Canada--Biography.
Princeton subject headings: