1. Al Shaibi, Y. M., & Hedi, L. (2006). Sana’a City: Medium to long-term city development strategy for sustainable development. Arab Urban Development Institute (AUDI).
2. Al-Ansi, A. (1998). Local Government, http://www.alhyat.ac.com .
3. Al-Ghabiry, A. (1999). The first Yemeni human development report launched. Yemen Times. V.30, August 1st.
4. Al-Haj, M. S. (2001). Environmental impact of urban expansion in Ibb city, Yemen: Application of GIS and Remote Sensing, PhD theses, University of Nottingham.
5. Al-Qubati, S. (2002). Spontaneous settlements phenomena & urban development- internal contrast in Yemeni cities, Journal of Aden University.