On Equations for the Multi-quark Bound States in Nambu--Jona-Lasinio Model

In present report we review some preliminary results of investigation of higher orders of mean-field expansion for Nambu--Jona-Lasinio model. We discuss first results of investigation of next-to-next-to-leading order of mean-field expansion equations for four-quark and three-quark Green functions. We have considered equations for Green functions of Nambu--Jona-Lasinio model in mean-field expansion up to third order.