International legend for hydrogeological maps = Leyenda internacional para mapas hidrogeológicos = Légende internationale des cartes hydrogéologiques = Mezhdunarodnai︠a︡ legenda k gidrogeologicheskim kartam.
Unesco.
[Paris,
1970]
English, French, Russian and Spanish.
Bibliography: 79-83.
Maps
Hydrogeology
Cartes géographiques
Hydrogéologie