RCS question

Hi. I have a question about the RCS (Radar Cross Section) unit. Some literature show that it is dBm^2, I am not sure how to get it?
Is it RCS=lim(r->∞)(4πr^2|Er^2|/|Ei^2|, I think the unit should be m^2?

Thanks in advance

Yes the unit is m^2, but often it is converted to dBsm (10*log10(RCS in m^2)). A good book on RCS is Balanis.