"We should, of course, expect that any universe which expands without limit will approach the empty de Sitter case, an…"

"The general theory of relativity considers physical space-time as a four-dimensional manifold whose line element coef…"

"An "empty world," i.e., a homogeneous manifold at all points at which equations (1) are satisfied, has, according to …"

"In considerations involving the nature of the world as a whole the irregularities caused by the aggregation of matter…"

"The solution of (1), which represents a homogeneous manifold, may be written in the form:ds^2 = \frac{d\rho^2}{1 - \k…"

"is a congruence geometry, or equivalently the space comprising its elements is homogeneous and isotropic; the intrins…"

"[O]nly in a homogeneous and isotropic space can the traditional concept of a rigid body be maintained."

"That the existence of these motions (the "axiom of free mobility") is a desideratum, if not... a necessity, for a geo…"

"Euclidean geometry is only one of several congruence geometries... Each of these geometries is characterized by a rea…"

"The value of the intrinsic approach is especially apparent in considering 3-dimensional congruence spaces... The intr…"