 
                            
                        
                        
                        A History of Greek Mathematics (1921) Vol. 1. From Thales to Euclid
            p, 125 
Achimedes (1920)
        
A History of Greek Mathematics (1921) Vol. 1. From Thales to Euclid
                                        
                                        this implies the use of similar triangles in the way that the Egyptians had used them in the construction of pyramids 
Achimedes (1920)
                                    
                                        
                                        The geometry of the spherical surface can be viewed as the realization of a two-dimensional non-Euclidean geometry: the denial of the axiom of the parallels singles out that generalization of geometry which occurs in the transition from the plane to the curve surface. 
The Philosophy of Space and Time (1928, tr. 1957)
                                    
