"USA" . . . . . "At the crossroads: the mineral problems of the United States" . . . . . . . . . "At the crossroads : the mineral problems of the United States" . . . . . . . "At the crossroads : the mineral problems of the united States" . . . . . . "At the Crossroads" . . "Geología económica Estados Unidos." . . "Rohstoffressourcen / Mineralölwirtschaft / Metallindustrie / USA." . . "USA." . . "Ressources minérales États-Unis." . . "Ressources minérales - États-Unis." . "Rohstoffressourcen" . . "Mineralischer Rohstoff." . . . . "Metallindustrie" . . "Minas Estados Unidos." . . "Mineralölwirtschaft" . .