“…Now for shortness, we introduce the notation as in Eremeev and Lebedev [34]: U = ( ( u , ϕ ) , u 1 ,… , u n , ϑ 1 ,… , ϑ N ) and, respectively, δ U = ( ( δ u , δ ϕ ) , δ u 1 ,… , δ u n , δ ϑ 1 ,… , δ ϑ N ) . On the set of U where ( u , f ) are smooth functions satisfying boundary conditions (9) 3 and (9) 4 , we introduce an inner product defined by the energy terms for ( u , ϕ ) :…”