  Strongly intensive measures $\Delta$ and $\Sigma$ are used to study
event-by-event fluctuations of hadron multiplicities in nucleus-nucleus
collisions. The effects of resonance decays are investigated within statistical
model and relativistic transport model. Two specific examples are considered:
resonance decays to two positively charged particles (e.g.,
$\Delta^{++}\rightarrow p+ \pi^+$) and to $\pi^+\pi^-$-pairs. (e.g.,
$\rho^0\rightarrow \pi^-+\pi^+$). It is shown that resonance abundances at the
chemical freeze-out can be estimated by measuring the fluctuations of the
number of stable hadrons. These model results are compared to the full
hadron-resonance gas analysis within both the grand canonical and canonical
ensemble. The ultra-relativistic quantum molecular dynamics (UrQMD) model of
nucleus-nucleus collisions is used to illustrate the role of global charge
conservation, centrality selection, and limited experimental acceptance.
