Instance of: http://www.w3.org/2004/02/skos/core#Concept
Subject Field unknown
Is Reference of Free surface-en#Sense
Saordhromchla-ga#Sense
Voľný povrch-sk#Sense
Laisvasis paviršius-lt#Sense
Surface libre-fr#Sense
Szabad felszín-hu#Sense