“…(1.71)], where one includes a Laplacian of qi in addition to the Mariano flux. Further relevant articles on this aspect are those of Rogolino & Cimmelli [59] and Carlomagno et al [60]. The relevant nonlinear perturbation equations are then right left right left right left right left right left right left3pt0em 2em 0em 2em 0em 2em 0em 2em 0em 2em 0emtrueui,t+ujui,j=−π,i+Δui+Rθki,ui,i=0,Pr(θ,t+uiθ,i)=Rw−qi,i+ζΔθ,Sg(qi,t+ujqi,j−ui,jqj)=RSgPr ui,3−qi−θ,i+ϵΔqi.The ϵ term in (7.1) is described by Ván & Fülöp [58] and by Mariano [<...…”