“…The notion of very weak solutions (u, q) ∈ L p (Ω)×W −1,p (Ω) for the stationary Stokes or Navier-Stokes equations, corresponding to very irregular data, has been developed in the last years by Giga [9] (and also by Lions-Magenes [11] for the Laplace's equation, in a domain Ω of class C ∞ ), Amrouche-Girault [1] (in a domain Ω of class C 1,1 ) and more recently by Galdi-Simader-Sohr [8], Farwig-Galdi-Sohr [7] (in a domain Ω of class C 2,1 , see also Schumacher [14]) and finally by Kim [10] (in a domain Ω of class C 2 with connected boundary). In this context, the boundary condition is chosen in L p (Γ) (see Brown-Shen [3], Conca [5], Fabes-Kenig-Verchota [6], Moussaoui [12], Shen [15], Savaré [13]) or more generally in W −1/p,p (Γ).…”