Authorization is not employer specific. Time limit is strict. INS approval takes time. Individual must have an academic appointment and sufficient financial support. Process is short and easy.
Waivers vary, depending on circumstances, from available but slow to unobtainable.
An academic appointment or invitation to the U of C and sufficient financial support. Process is short and easy. Short-term scholar category is good for lectures, symposia, etc. Allows payment of honoraria. Waivers vary, depending on circumstances, from available but slow to unobtainable.