Arbetmen, Lee P., author
West Publishing, 1990
Buku Teks
Garbutt, John, author
John Wiley & Sons, 1995
Buku Referensi
Topham, Alfred F.
Stevens and Sons, Limited, 1933
Buku Teks
Erich P. Prien, editor
Pfeiffer, 2009
Buku Teks
Darryl J. Cooke
FT Law & Tax, 1997
Buku Teks