@MirAkhArefITW10; @MariYatKra06]. For an overview on the capacity results of C-IFC, see [@RiniIT11].

The *$k$-user* IFC consists of $k$ independent transmitters sending messages to $k$ independent receivers. Extending the results of the classic two-user IFC to the IFCs with more than two user pairs is non-trivial; because each receiver is affected by the joint interference from the all other transmitters rather by each transmitter’s signal separately [@ElgKim11 P. 157]. Recently, the capacity region of a three-user Gaussian IFC under mixed strong-very strong interference conditions has been characterized in [@ChaSez10]. In C-IFC, asymmetric nature of the transmitters’ cooperation makes this extension even more challenging, since there are several ways for applying the cognition capabilities and also the obtained setups may involve different aspects of IFCs such as independent channel inputs at the transmitters which makes difficult to apply the results of C-IFC to these setups. An achievable rate region for a three-user Multiple Access Channel (MAC) [@ElgKim11 Chapter 4] with three transmitters and *one receiver* has been derived in [@NagKis_Gl10]. By increasing the number of receivers, a *three-user* C-IFC with *one* primary user and *two* cognitive users has been studied in [@NagMur_ITW09; @NagMur_Gl09], where an achievable rate region is derived for 