Sequential games and Perfect Bayesian Equilibrium
As Fudenberg and Tirole note, the fact that they assume players move simultaneously does not matter:


  This specification is more general than
  it may appear, because the set of feasible actions can be time and history
  dependent, so that games with alternating moves are included.


Moreover, all actions are observable by all players, so the definition would be unchanged by the assumption that moves are alternating.