[2] P. R. Halmos:
Measure Theory. D. van Nostrand Comp., Inc., Toronto, New York, London 1951.
MR 0033869
[3] H. Rasiowa R. Sikorski:
The Mathematics of Metamathematics. Third Edition, PWN, Warszawa 1970.
MR 0344067
[4] R. Sikorski:
Boolean Algebras. Second Edition, Springer Verlag, Berlin-Göttingen-Heidelberg-New York 1964.
Zbl 0123.01303