@article {RicKor-ENGC-2000,
	title = {Euklidische und nicht-{E}uklidische {G}eometrie in {C}inderella},
	journal = {Journal f{\"u}r Mathematikdidaktik},
	volume = {22},
	year = {2000},
	pages = {303{\textendash}324},
	abstract = {<p>
	Zusammenfassung: Wir erinnern an die Konzeption euklidischer und nicht-euklidischer Geometrie durch Klein und Cayley und weisen auf ihre Bedeutung fu ̈r moderne Software zur interaktiven (oder dynamischen) Geometrie hin. Insbesondere zeigt es sich, dass sich komplexe Zahlen vorzu ̈glich zu einer allgemein Behandlung hyperbolischer, elliptischer, euklidischer und anderer Geometrie eignen. Summary: We recall the concepts of Euclidean and non-Euclidean Geometry in the sense of Klein and Cayley and illustrate their importance for modern interactive (dynamic) geometry software. In particular, the use of complex numbers turns out to be the key to the most general approach to measurements in hyperbolic, elliptic, Euclidean and other geometries.</p>
},
	keywords = {refereed},
	url = {http://kortenkamps.net/papers/2000/Euklidisch-NichtEuklidisch.pdf},
	author = {Richter-Gebert, J{\"u}rgen and Kortenkamp, Ulrich}
}
@conference {KorRic-ENGC-1999,
	title = {Euklidische und {N}icht-{E}uklidische {G}eometrie mit {C}inderella},
	booktitle = {Tagungsband zum N{\"u}rnberger Kolloquium zur Didaktik der Mathematik 1999},
	year = {1999},
	keywords = {invited},
	url = {http://www.inf.fu-berlin.de/~kortenka/Papers/nichtEuklidisch.pdf},
	author = {Kortenkamp, Ulrich H. and Richter-Gebert, J{\"u}rgen},
	editor = {Weth, Thomas}
}
@article {KorRicSarZie-EP0-1997,
	title = {Extremal properties of 0/1-polytopes},
	journal = {Discrete \& Computational Geometry},
	volume = {17},
	year = {1997},
	pages = {439{\textendash}448},
	abstract = {<p>
	We provide lower and upper bounds for the maximal number of facets of a d-dimensional 0/1-polytope, and for the maximal number of vertices that can appear in a two-dimensional projection ("shadow") of such a polytope.</p>
},
	keywords = {refereed},
	url = {http://link.springer.de/link/service/journals/00454/htabst/17n4p439.html},
	author = {Kortenkamp, Ulrich and Richter-Gebert, J{\"u}rgen and Sarangarajan, A. and Ziegler, G{\"u}nter M.}
}
