The following are some suggested links for further study on the subject of the Deesis Mosaic, Hagia Sophia, Byzantium and Orthodoxy:
Pantokrator Monastery - Zeyrek Djami
Dumbarton Oaks
Hagia Sophia - Little Chronicle of a Great Church
The Novo-Tikvin Woman's Monastery in Yekaterinburg
Egg Tempera Forum
Iconofile Forum for Icons and Sacred Art
Pandora Icon Boards
Alexander Palace Time Machine
Bob Ousterhout's Constantinople Website
Father Serfes Site on the Royal Russian Martyrs
Ikons - Windows into Heaven
Orthodox Church in America
Download a PDF on The Conservation of the Dome Mosaics of Hagia Sophia