%0 Journal Article
%A Borislav Lazarov
%T Teaching envelopes in secondary school
%J The Teaching of Mathematics
%D 2011
%P 45 
%V XIV
%N 1
%I mathdoc
%U http://geodesic.mathdoc.fr/item/TM2_2011_XIV_1_a3/
%G en
%F TM2_2011_XIV_1_a3