@article{NUMA_1968__12_131873,
     author = {P.G. CIARLET and R.S. VARGA and M.H. SCHULTZ},
     title = {Numerical {Methods} of {High-Order} {Accuracy} for {Nonlinear} {Boundary} {Value} {Problems.} {IV.} {Periodic} {Boundary} {Conditions.}},
     journal = {Numerische Mathematik},
     pages = {266--279},
     publisher = {mathdoc},
     volume = {12},
     year = {1968},
     zbl = {0181.18303},
     url = {http://geodesic.mathdoc.fr/item/NUMA_1968__12_131873/}
}