@conference {19822,
	title = {Abstraction through instrumentalization},
	booktitle = {Proceedings of the 37th Conference of the International Group for the Psychology of Mathematics Education (PME 37), Research forum {\textquotedblleft}Activity theoretical approaches to mathematics classroom practices with the use of technology{\textquotedblright}},
	volume = {1},
	year = {2013},
	pages = {192-196},
	publisher = {PME},
	organization = {PME},
	address = {Kiel, Germany},
	author = {G Psycharis},
	editor = {A M Lindmeier and A Heinze}
}
