  In this paper, we derive the Ewald method for inverse power-law interactions
in quasi-two dimensional systems. The derivation is done by using two different
analytical methods. The first uses the Parry's limit, that considers the Ewald
methods for quasi-two dimensional systems as a limit of the Ewald methods for
tridimensional systems, the second uses Poisson-Jacobi identities for lattice
sums. Taking into account the equivalence of both derivations, we obtain a new
analytical Fourier transform intregral involving incomplete gamma function.
Energies of the generalized restrictive primitive model of electrolytes
($\eta$-RPM) and of the generalized one component plasma model ($\eta$-OCP) are
given for the tridimensional, quasi-two dimensional and monolayers systems. Few
numerical results, using Monte-Carlo simulations, for $\eta$-RPM and $\eta$-OCP
monolayers systems are reported.
