“…In addition to choosing the interpolation-type MLS methods, some mandatory methods, such as the Lagrange multiplier method [ 3 , 4 , 13 ], Nitsche method [ 22 , 23 ] and penalty method [ 3 , 4 , 24 , 25 , 26 , 27 , 28 ] are desirable in practical applications. The important feature of these methods is that they can straightforwardly use the non-interpolating trial and test functions by modifying the traditional weak form.…”