http://halisway.blogspot.com/2006/04/sql-connect-by.html

http://download-uk.oracle.com/docs/cd/B19306_01/server.102/b14200/statements_10002.htm#sthref9844

http://www.java2s.com/Code/Oracle/Hierarchical-Query/HierarchicalQueriesSTARTWITHandCONNECTBYPRIORclauses.htm