  We provide a new, simple general proof of the formulas giving the infinite
sums $\sigma(p,\nu)$ of the inverse even powers $2p$ of the zeros $\xi_{\nu k}$
of the regular Bessel functions $J_{\nu}(\xi)$, as functions of $\nu$. We also
give and prove a general formula for certain linear combinations of these sums,
which can be used to derive the formulas for $\sigma(p,\nu)$ by purely
linear-algebraic means, in principle for arbitrarily large powers. We prove
that these sums are always given by a ratio of two polynomials on $\nu$, with
integer coefficients. We complete the set of known formulas for the smaller
values of $p$, extend it to $p=9$, and point out a connection with the Riemann
zeta function, which allows us to calculate some of its values.
