  We prove optimal order error estimates for the Raviart-Thomas interpolation
of arbitrary order under the maximum angle condition for triangles and under
two generalizations of this condition, namely, the so-called three dimensional
maximum angle condition and the regular vertex property, for tetrahedra.
  Our techniques are different from those used in previous papers on the
subject and the results obtained are more general in several aspects. First,
intermediate regularity is allowed, that is, for the Raviart-Thomas
interpolation of degree $k\ge 0$, we prove error estimates of order $j+1$ when
the vector field being approximated has components in $W^{j+1,p}$, for
triangles or tetrahedra, where $0\le j \le k$ and $1\le p \le\infty$. These
results are new even in the two dimensional case. Indeed, the estimate was
known only in the case $j=k$. On the other hand, in the three dimensional case,
results under the maximum angle condition were known only for $k=0$.
