  BeppoSAX observations of the single pulse burst GRB960720 have allowed a
detailed study of its X-ray properties: pulse width in different energy bands,
spectral evolution from 2 to 700 keV, etc. We show that the early (0-5s) X-ray
emission and the gamma-rays are well explained by internal shocks in a
relativistic wind while the late (5-20s) X-ray emission could come from the
reverse shock generated in the wind when it interacts with the external medium.
The results for a medium of uniform density are compared to the observations.
