Read about Palmyra's revolt and Zenobia's rule over the eastern part of
the Roman empire in Jacqueline Long's biography
of Vaballathus and Zenobia, from DIR's On-line Encyclopedia of Roman Emperors
Uses and Meaning of Palmyran Sculpture, part of a larger site that includes discussions of characteristics, iconography, and comparison of Palmyran sculpture with Roman sculpture (USC)
Excerpts from David Kennedy and Derrick Riley. Rome's
Desert Frontier. University of Texas Press, Austin, 1990 (once there,
from the Menu bar, click on Edit, then Find in Page and you will find the
sections that discuss Palmyra)