Assertion: abelian group's element | /r/HasProperty | vertical
Facets:
Source sentences:
text: The four elements of D(x-axis is vertical here)
text: Geometrically, in two dimensions the Klein four-group is the symmetry group of a rhombus and of rectangles that are not squares, the four elements being the identity, the vertical reflection, the horizontal reflection, and a 180 degree rotation.