>  (breadth-first 'newark 'san-francisco)
Extending the path (newark)
Extending the path (newark indianapolis)
Extending the path (newark orlando)
Extending the path (newark manchester)
Extending the path (newark beijing)
Extending the path (newark indianapolis chicago-midway)
Extending the path (newark indianapolis ft-lauderdale)
Extending the path (newark orlando chicago-midway)
Extending the path (newark orlando dallas-ftworth)
Extending the path (newark orlando miami)
Extending the path (newark manchester bwi)
Extending the path (newark manchester providence)
Extending the path (newark manchester hartford)
Extending the path (newark manchester bar-harbor)
Extending the path (newark manchester montreal)
Extending the path (newark beijing hong-kong)
Extending the path (newark beijing tokyo)
Extending the path (newark beijing los-angeles)
Final path length is 3

Proceed from newark to beijing
then from beijing to san-francisco.
((san-francisco beijing newark))