1. P. HAUTOJÄRVI (Ed.), in: Positron in Solids Springer-Verlag, Berlin, Heidelberg, New York, 1979, p. 1.
2. J. R. STEVENS, in: Methods of Experimental Physics, Vol. 16A, 1980, p. 371.
3. Y. C. JEAN, D. M. SCHRADER, in: Positron and Positronium Chemistry, Elsevier, Amsterdam, 1988, p. 91.
4. H. J. ACHE, in: Positron and Positronium Chemistry, Elsevier, Amsterdam, 1988, p. 318.
5. Y. C. JEAN, Microchem. J., 42 (1990) 72.