@book{2487, author = {Agor, R.}, title = {A textbook of Surveying and Levelling}, publisher = {Khanna Publisher.}, year = {2016.}, address = {Delhi :}, edition = {12th ed.}, url = {https://books.google.com.pk/books?id=TnehkgEACAAJ&dq=A+textbook+of+surveying+and+levelling+R+agor&hl=en&sa=X&redir_esc=y} }