@ARTICLE {, title = {Matematické nástroje - Zjednodušenie. Substitúcia}, author = {Vrábel, Peter}, journal = {Obzory matematiky, fyziky a informatiky}, year = {2007}, volume = {36}, number = {4}, pages = {27--30}, issn = {1335-4981}, abstract = {The use of mathematical tool simplification is illustrated on solutions of various tasks in the paper.}, }