The problem as to whether or not there exists a lifting of the M't/. 1
space ) corresponding to the real line and Lebesgue measure on it was
first raised by A. Haar. It was solved in a paper published in 1931
[102] by 1. von Neumann, who established the existence of a lifting in
this case. In subsequent papers J. von Neumann and M. H. Stone [105],
and later on 1. Dieudonne [22], discussed various algebraic aspects
and generalizations of the problem. Attemps to solve the problem as to
whether or not there exists a lifting for an arbitrary M't/. space were
unsuccessful for a long time, although the problem had significant
connections with other branches of mathematics. Finally, in a paper
published in 1958 [88], D. Maharam established, by a delicate
argument, that a lifting of M't/. always exists (for an arbi- trary
space of a-finite mass). D. Maharam proved first the existence of a
lifting of the M't/. space corresponding to a product X = TI {ai, b, }
ieI and a product measure J.1= Q9 J.1i' with J.1i{a;}=J.1i{b, }=! for
all iE/., eI Then, she reduced the general case to this one, via an
isomorphism theorem concerning homogeneous measure algebras [87],
[88]. A different and more direct proof of the existence of a lifting
was subsequently given by the authors in [65]' A variant of this proof
is presented in chapter 4.