  This 1995 paper contains a sharp version of the classical Marcinkiewicz
multiplier theorem for the class of homogeneous Fourier multipliers in two
dimensions; here a one-dimensional Marcinkiewicz condition is sufficient.
Examples are given to show that the straightforward extension of this statement
to higher dimensions does not hold. We provide appropriate versions in higher
dimensions which rely on a Fefferman-Stein weighted norm inequality for a
relevant C\'ordoba type square function. The proof of this inequality is given
by an early version of an induction on scales argument. For $p<1$ we prove a
multiplier theorem on product-type $H^p$-spaces.
