@article{SJC_2015_9_3-4_a6,
     author = {Kenderov, Petar and Chehlarova, Toni},
     title = {Extending the {Class} of {Mathematical} {Problems} {Solvable} in {School}},
     journal = {Serdica Journal of Computing},
     pages = {191--206},
     publisher = {mathdoc},
     volume = {9},
     number = {3-4},
     year = {2015},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SJC_2015_9_3-4_a6/}
}