@article{10_21136_MB_2014_143853,
     author = {Manko, Stepan},
     title = {Quantum-graph vertex couplings: some old and new approximations},
     journal = {Mathematica Bohemica},
     pages = {259--267},
     publisher = {mathdoc},
     volume = {139},
     number = {2},
     year = {2014},
     doi = {10.21136/MB.2014.143853},
     mrnumber = {3238838},
     zbl = {06362257},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.21136/MB.2014.143853/}
}