An inhomogeneous Lax representation for the Hirota equation
  Motivated by recent work on quantum integrable models without U(1) symmetry, we show that the sl(2) Hirota equation admits a Lax representation with inhomogeneous terms. The compatibility of the auxiliary linear problem leads to a new consistent family of Hirota-like equations. 
Davide Fioravanti and Rafael I. Nepomechie
math-ph hep-th math.MP