@article{TM2_2006_IX_2_a1,
     author = {Martti E. Pesonen and Lenni Haapasalo and Timo Ehmke},
     title = {Critical look at dynamic sketches when learning mathematics},
     journal = {The Teaching of Mathematics},
     pages = {19 },
     publisher = {mathdoc},
     volume = {IX},
     number = {2},
     year = {2006},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/TM2_2006_IX_2_a1/}
}