Gaya APA
Havers, J, A., Jr., F, W, S. (1971).
Handbook of Heavy Construction (Second Edition).
United States of America:
The Mcgraw-hill Companies.
Gaya MLA
Havers, John, A.., Jr., Frank, W., Stubbs,.
"Handbook of Heavy Construction".
Second Edition
United States of America:
The Mcgraw-hill Companies,
1971.
REF.