1. Many references to the subject may be found in:J. Green andJ. Lee:Positronium Chemistry (New York, 1964).
2. R. E. Green andR. E. Bell:Canad. Journ. Phys.,35, 398 (1957).
3. V. I. Gol’danskiì, T. A. Solonyenko andV. P. Shantarovich:Dokl. Acad. Nauk. S.S.S.R.,151, 608 (1963).
4. G. Trumpy:Phys. Rev.,110, 668 (1960).
5. V. I. Gol’danskiì, I. H. Karpukhin andG. G. Petrov:Sov. Phys. JETP,12, 1026 (1961).