1. Alsam SI, Saad ZJ, Hanna F (1990) Water balance of Iraq: stage 2, geological and hydrological conditions. Manuscript report. Ministry of Irrigation, Iraq
2. Bridgman HA, Oliver JE (2006) The global climate system. Cambridge University press, New York
3. Buchdahl J (1999) Global Climatic Change, student guide. A review of contemporary and prehistoric global climatic change. Manchester Metropolitan University. p 99 http://cdiac.org.gov
4. Lean J, Rind D 1996 The Sun and climate. Consequences Vol. 2, No. 1, Winter
5. Petit JR, Jousel J et al (1999) Climate and atmospheric history of the past 420, 000 years from the Vostok ice core, Antarctica. Nature 399:420–436