On Theta Characteristics
IMAGE- Saavedra-Rivano, 'Finite Geometries in the Theory of Theta Characteristics' (1976)
— From Zentralblatt-math.org.  8 PM ET update:  See also a related search.
IMAGE- Saavedra-Rivano, Ph.D. U. de Paris 1972, advisor Grothendieck
Some may prefer a more politically correct— and simpler— sermon.
Background for the simpler sermon: Quilt Geometry.