Occurrence of Attributes in Original Text

The text related to the cultural heritage 'Carlsbad Caverns National Park' has mentioned 'Wood' in the following places:

Occurrence Sentence	Text Source
Using a balsa wood loop with helium-filled balloons attached, the explorers, (after several tries over several years), floated a lightweight cord up, over the target stalagmite, and back down to the ground.	WIKI