1. lectures given at the School on Light-Front Quantization and Non-Perturbative Dynamics — Theory of Hadrons and Light-Front QCD;Burkardt,1996
2. International Conference on Orbis Scientiae (1996), Miami Beach, Florida;Brodsky,1996
3. School on Light-Front Quantization and Non-Perturbative Dynamics — Theory of Hadrons and Light-Front QCD;Burkardt,1996
4. D.G. Robertson, The vacuum in light-cone field theory, OHSTPY-HEP-T-96-011 preprint A.C. Kalloniatis and D.G. Robertson, θ vacua in the light-cone Schwinger model, OSU-NT-95-07 preprint.