On multiplicity functions and Lebesgue area
Rendiconti del Seminario Matematico della Università di Padova, Tome 42 (1969), pp. 201-207. 
@article{RSMUP_1969__42__201_0,
     author = {Schaefer, D. J.},
     title = {On multiplicity functions and {Lebesgue} area},
     journal = {Rendiconti del Seminario Matematico della Universit\`a di Padova},
     pages = {201--207},
     publisher = {Seminario Matematico of the University of Padua},
     volume = {42},
     year = {1969},
     zbl = {0234.28011},
     mrnumber = {276444},
     language = {en},
     url = {http://www.numdam.org/item/RSMUP_1969__42__201_0/}
}
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Schaefer, D. J. On multiplicity functions and Lebesgue area. Rendiconti del Seminario Matematico della Università di Padova, Tome 42 (1969), pp. 201-207. http://www.numdam.org/item/RSMUP_1969__42__201_0/

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