1. R.L. Walker, B.L. Berman, R.C. Der, T.M. Kavanagh, Ü.M. Khan: Phys. Rev. Lett. 25, 5 (1970). This experiment was essentially duplicated, with 1-GeV positrons and electrons, by
2. V.L. Morikhovskii, G.D. Kovalenko, I.A. Grishaev, A.N. Fisun, V.I. Kasilov, B.I. Shramenko, A.N. Krinitsyn: Pis’ma Zh. Eksp. Teor. Fiz. 16, 162 (1972)
3. V.L. Morikhovskii, G.D. Kovalenko, I.A. Grishaev, A.N. Fisun, V.I. Kasilov, B.I. Shramenko, A.N. Krinitsyn: [English transl.: JETP Lett. 16, 112 (1972)]. They, too, observed channeling radiation, but this fact has not been recognized until now.
4. R.L. Walker, B.L. Berman, S.D. Bloom: Phys. Rev. A11, 736 (1975). Low-energy enhancement like that seen in this experiment has also been seen with 800-MeV electrons by
5. S.A. Vorobiev, B.N. Kalinin, V.V. Kaplin, A.P. Potylitsin: Pis’ma Zh. Tekh. Fiz. 4, 1340 (1978)