@article{PNA_2009_2009_1_a1,
     author = {Cusi, Annalisa and  Malara, Nicolina A.},
     title = {Improving {Awareness} about the {Meaning} of the {Principle} of {Mathematical} {Induction.}},
     journal = {PNA},
     pages = {15-22},
     publisher = {mathdoc},
     volume = {4},
     number = {1},
     year = {2009},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/PNA_2009_2009_1_a1/}
}