@inbook{1452dc5f4c134f3e98a63a85ec04faa9,
title = "Number Pyramids as a Mathematically Rich Learning Environment for All Students",
keywords = "Didactics of Mathematics, Rechenoperationen, fr{\"u}he Algebra, Grundschule",
author = "Silke Ruwisch and Torsten Fritzlar",
year = "2014",
language = "English",
isbn = "978-0-87353-744-5",
pages = "33--41",
editor = "Lott, \{Johnny W.\} and Lott, \{Carolyn J.\}",
booktitle = "Mathematics Lessons Learned from Across the World",
publisher = "National Council of Teachers of Mathematics ",
address = "United States",
}