  Answering a question of A.Zygmund in \cite{MR} G.MacLane and L.Rubel
described boundedness of $L_2$-norm w.r.t. the argument of $\log |B|$, where
$B$ is a Blaschke product. We generalize their results in several directions.
We describe growth of $p$th means, $p\in(1, \infty)$, of subharmonic functions
bounded from above in the unit disc. Necessary and sufficient conditions are
formulated in terms of the complete measure (of a subharmonic function) in the
sense of A.Grishin. We also prove sharp estimates of the growth of $p$th means
of analytic and subharmonic functions of finite order in the unit disc.
