@article{MS2_1993__72_1_167245,
     author = {E. Poletaeva},
     title = {Penrose's tensors. {II.}},
     journal = {Mathematica Scandinavica},
     pages = {191--211},
     publisher = {mathdoc},
     volume = {72},
     number = {1},
     year = {1993},
     zbl = {0791.53036},
     url = {http://geodesic.mathdoc.fr/item/MS2_1993__72_1_167245/}
}