1. Free mobility and orthogonality;Baer;Trans. Am. Math. Soc.,1950
2. Metric foundations of geometry;Birkhoff,1941
3. Metric foundations of geometry I;Birkhoff;Trans. Am. Math. Soc.,1944
4. Extensions of Lie groups;Birkhoff;Math. Z.,1950
5. History of the octaves;van der Blij;Simon Stevin,1961