You can do simple searches using this form:

Type	Originator	Title	Date
	Gies,J	Adventure underground: the story of the world's great tunnels	1962
	Errand,J	Secret Passages and Hiding Places	1974
	Pennick,N	The Subterranean Kingdom	1981
	Mangold,T & Penycate,J	The Tunnels of Cu Chi	1986