VISITOR

accept(Visitor visitor) { visitor.visit(this); } } class Engine { void accept(Visitor visitor) { visitor.visit(this); } } class Body { void accept(Visitor visitor)

Matthew; Huntington, Indiana, U. S. (2004). OSV's Encyclopedia of Catholic History (2nd ed.). Our Sunday Visitor Publishing Division. ISBN 1-59276-026-0.

Sawtooth National Forest, U.S. Forest Service.  Sawtooth National Forest Visitor Guide (PDF). U.S. Forest Service. [2012-05-09]. （原始内容 (PDF)存档于2013-02-12）

大英铁路博物馆 国立媒体博物馆 VISITS MADE IN 2008 TO VISITOR ATTRACTIONS IN MEMBERSHIP WITH ALVA. Association of Leading Visitor Attractions. 2009-02-26 [2009-03-16]

Visits made in 2012 to visitor attractions in membership with Alva. Association of Leading Visitor Attractions. [2010-05-21]. （原始内容存档于2016-03-07）