books?id=U-88Xa-lm_gC&pg=PA124&lpg=PA124&dq=%22nubian+vault%22+architecture&source=bl&ots=4MT5bPcASD&sig=TDtjy36RZYRNUFWCtpGOFFeqvwc&hl=en&ei=3W9OSoHoBYyOtAPhp_CqDQ&sa=X&oi=book_result&ct=result&resnum=2

books?id=U-88Xa-lm_gC&pg=PA124&lpg=PA124&dq=%22nubian+vault%22+architecture&source=bl&ots=4MT5bPcASD&sig=TDtjy36RZYRNUFWCtpGOFFeqvwc&hl=en&ei=3W9OSoHoBYyOtAPhp_CqDQ&sa=X&oi=book_result&ct=result&resnum=2

http://books.google.com/books?id=U-88Xa-lm_gC&pg=PA124&lpg=PA124&dq=%22nubian+vault%22+architecture&source=bl&ots=4MT5bPcASD&sig=TDtjy36RZYRNUFWCtpGOFFeqvwc&hl=en&ei=3W9OSoHoBYyOtAPhp_CqDQ&sa=X&oi=book_result&ct=result&resnum=2
Nubian vault
Link from a Wikipage to an external page

books?id=U-88Xa-lm_gC&pg=PA124&lpg=PA124&dq=%22nubian+vault%22+architecture&source=bl&ots=4MT5bPcASD&sig=TDtjy36RZYRNUFWCtpGOFFeqvwc&hl=en&ei=3W9OSoHoBYyOtAPhp_CqDQ&sa=X&oi=book_result&ct=result&resnum=2

http://books.google.com/books?id=U-88Xa-lm_gC&pg=PA124&lpg=PA124&dq=%22nubian+vault%22+architecture&source=bl&ots=4MT5bPcASD&sig=TDtjy36RZYRNUFWCtpGOFFeqvwc&hl=en&ei=3W9OSoHoBYyOtAPhp_CqDQ&sa=X&oi=book_result&ct=result&resnum=2