1. Allan, A. L. 1993. Practical surveying and computations. Second Edition. Butterworth Heinemann, London. 573 pages .
2. Allan, A. L., Hollwey, J. R. and Maynes, J. H. B. 1968. Practical field surveying and computations Heinemann, London. 689 pages.
3. Becker, T., and Weispfenning, V. 1993. Groebner bases. A computational approach to commutative algebra Graduate Text in Mathematics 141. Springer-Verlag, New York. 574 pages.
4. Becker, T., and Weispfenning, V. 1998. Groebner bases. A computational approach to commutative algebra. Graduate Text in Mathematics 141. Second Edition. Springer-Verlag, New York. 574 pages