1- Biddle , G.A. (1958), The Text book of field Astronomy, Her Majesty’s Stationary Office. London England.
2- Breed. C.B.G.L. Hosmer. And A.J. Bone (1962), Higher Surveying, Vol. II. 8th ed. John Wiley and Sons. Inc. New York, P. 159.
3- Buckner, R.Ben, (1975), “Reasons and Method for Accurate Direction in Land Surveys. “Journal of the Surveying and Mapping Division, ASCE (Dec.)
4- Buckner, R,Ben. (1984). Manual on Astronomic and Grid Azimuth, Landmark Enterprises.
5- Department Of the Army (1970), “Precise Astronomuc Surveys Technival Manual TM5, 442. Washington, D.C. paras. 8-10.
6- Deumlich, Fitz (1982), Surveying instruments. Walter de Gruyter.,Berlin and New York, pp. 128-129.
7- Hoskinson, A and J. Duerksen (1952), “Manual of Geodetic Astronomy, “Special Publication 237,U.S. Coast and Geodetic Survey. Washington. D.G., pp.92-93.
8- Mackie, J.B (1978). Astronomy for Surveyors, 8th ed., Charles Griffin and Co.. Ltd. London.
9- Mueller. Ivan.I. (1969) , Spherical and Practical Astronomy ad Applied to Geodesy . Frederik Ungar Publishing Co., New York, pp. 312-313 and ch.9.