@article{AFM_1969_421-450_a23,
     author = {VJ. Nummi},
     title = {Operator-operand languages},
     journal = {Annales Fennici Mathematici},
     publisher = {mathdoc},
     volume = {421-450},
     year = {1969},
     doi = {10.5186/aasfm.1969.427},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.5186/aasfm.1969.427/}
}