Columbia subject headings:
Harvard subject headings:
Environmental protection--Spain--Majorca--History--Congresses.
Explorers--Mediterranean Region--Biography--Congresses.
Ludwig Salvator, Archduke of Austria, 1847-1915--Congresses.
Ludwig Salvator, Archduke of Austria, 1847-1915--Knowledge--Landscapes--Congresses.
Ludwig Salvator, Archduke of Austria, 1847-1915--Travel--Congresses.
Mediterranean Region--Description and travel--Congresses.
Scientific expeditions--History--19th century--Congresses.
Princeton subject headings:
Environmental protection--Spain--Majorca--History.
Ludwig Salvator, Archduke of Austria, 1847-1915.