How did (2+1) KP equation derived from Sato theory?

581 Views Asked by At

In section "Connection with Sato theory" of webpage scholarpedia they discussed that KP equation can be derived from taking a pseudo-differential operator $L$ and consider the differential equation $dL/dt_m=[(L^m)_{+},L]$. So how did this carried out? Especially what's the relationship between $L$ and $u$?