[1] W. W. COMFORT S. NEGREPONTIS: 
The theory of ultrafilters. Berlin - Heidelberg - New York, Springer 1974. 
MR 0396267[2] Z. FROLÍK J. PACHL: 
Pure measures. Comment. Math. Univ. Carolinae 14 (1973), 279-293. 
MR 0344399[3] J. PACHL: 
Every weakly compact  probability is compact. Bull. Acad. Polon. Sci., Sér. Math. Astronom. Phys. 23 (1975), 401-405. 
MR 0382577 | 
Zbl 0305.28001