show which set of experiments can be used to retrieve the tensor polarizability $\boldsymbol{\alpha}$. We find that magneto-electric coupling directly implies circular dichroism in the extinction of single split rings, evidencing the utility of our theory to describe structural chirality [@Gansel09; @Plum09; @Plum09b; @Zhang09; @Wang09; @plum07; @decker07; @decker10]. Thirdly, we show in Section \[section:coupledSRR\] that the theory can be simply applied to obtain quantitative scattering spectra of coupled systems. By way of example we examine the case of two coupled resonators in the stereodimer configuration reported by Liu et al. [@Giessen09].

Magneto-electric point scatterer\[section:generaltheory\]
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Polarizability
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A paradigm in scattering theory is the point dipole scatterer [@Lagendijk96; @Pedro98; @Weber04; @Koenderink06; @Abajo07] to model scattering by very small, but strongly scattering particles. Generally, incident fields $\bm{E}$ and $\bm{H}$ induce a (complex) current distribution in an arbitrary scatterer. It is the express point of this paper to assess what the scattering properties are of subwavelength scatterers with strong electric and magnetic dipole moments, as this represents the physics expected of metamaterial building blocks [@Garcia-Garcia05; @Sersic09; @Giessen09; @Feth10; @guo07]. Therefore we retain only electric and magnetic dipole terms, neglecting higher order multipoles. In such a theory, each scatterer is approximated as an 