Columbia subject headings:
Booksellers and bookselling--Europe--Colportage, subscription trade, etc.--History--Congresses.
Popular literature--Europe--History and criticism--Congresses.
Harvard subject headings:
Books and reading--Europe--Sociological aspects--Congresses.
Booksellers and bookselling--Europe--Colportage, subscription trade, etc.--History--Congresses.
Peddling--Europe--History--Congresses.
Popular literature--Europe--History and criticism--Congresses.
Popular literature--Europe--History--Congresses.
Street literature--Europe--History--Congresses.
Princeton subject headings:
Booksellers and bookselling--Europe--Colportage, subscription trade, etc.--History--Congresses.
Popular literature--Europe--History and criticism--Congresses.