APA
PIARC [Permanent International Association of Road Congresses]. World road congress, . (1951). PIARC. Paris: PIARC [Permanent International Association of Road Congresses]. World road congress.
Chicago
PIARC [Permanent International Association of Road Congresses]. World road congress, . 1951. PIARC. Paris: PIARC [Permanent International Association of Road Congresses]. World road congress.
Harvard
PIARC [Permanent International Association of Road Congresses]. World road congress, . (1951). PIARC. Paris: PIARC [Permanent International Association of Road Congresses]. World road congress.
MLA
PIARC [Permanent International Association of Road Congresses]. World road congress, . PIARC. Paris: PIARC [Permanent International Association of Road Congresses]. World road congress. 1951.