Grötschel, M.; Lovász, L.; and Schrijver, A. "The Ellipsoid Method and Its Consequences in Combinatorial Optimization."
Combinatorica1, 169-197, 1981.Knuth, D. E. "The
Sandwich Theorem." Electronic J. Combinatorics1, No. 1,
A1, 1-48, 1994. http://www.combinatorics.org/Volume_1/Abstracts/v1i1a1.html.
Sangaku problems, often written "san gaku," are geometric problems of the type found on devotional mathematical wooden tablets ("sangaku") which were hung under the roofs of shrines or temples in Japan during two centuries of schism from the West (Fukagawa and Pedoe 1989). During the time of isolation, Japanese mathematicians developed their own "traditional mathematics," which, in the 1850s, began giving way to Western methods. There were also changes in the script in which mathematics was written and, as a result, few people now living know how to interpret the historic tablets (Kimberling).
Japanese mathematicians represented in sangaku include Seki Kowa (1642-1708), Ajima Chokuen (also called Naonobu; 1732-1798), and Shoto Kenmotu (1790-1871).
of a graph 
satisfies
is the clique number, 
is the chromatic number
of 
,
and 
is the graph complement of 
. This can be rewritten by changing the role of graph complements,
giving
with 
the independence number and 
the clique
covering number as
can be computed efficiently despite the fact that the computation of the two numbers
it lies between is an NP-hard problem.
