Columbia subject headings:
Harvard subject headings:
Aeronautical engineers--Spain--Biography.
Balloonists--Spain--Biography.
Generals--Spain--Biography
Herrara, Emilio, 1879-1967.
Herrera, Emilio, 1879-1967.
Princeton subject headings:
Balloonists--Spain--Biography.
Herrara, Emilio, 1879-1967.