Gaya APA
Libby, J, R., Perkins, N, D. (1976).
Modern Prestressed Concrete Highway Bridge Superstructures .
California:
Grantville.
Gaya MLA
Libby, James, R.., Perkins, Norman, D..
"Modern Prestressed Concrete Highway Bridge Superstructures".
California:
Grantville,
1976.
Text.