@article{CM_1976__33_1_3_0,
     author = {Gorton, R.},
     title = {$A$-systems},
     journal = {Compositio Mathematica},
     pages = {3--13},
     publisher = {Noordhoff International Publishing},
     volume = {33},
     number = {1},
     year = {1976},
     mrnumber = {435264},
     zbl = {0338.20091},
     language = {en},
     url = {http://www.numdam.org/item/CM_1976__33_1_3_0/}
}