Here is a list of all namespace variables with links to the namespace documentation for each variable:

PAPER_NAME_A3 : Gtk
PAPER_NAME_A4 : Gtk
PAPER_NAME_A5 : Gtk
PAPER_NAME_B5 : Gtk
PAPER_NAME_EXECUTIVE : Gtk
PAPER_NAME_LEGAL : Gtk
PAPER_NAME_LETTER : Gtk