Dorit S. Hochbaum Instant recognition of polynominal time solvability, half integrality and 2-approximations. 2-14 http://link.springer.de/link/service/series/0558/bibs/1913/19130002.htm 2000 conf/approx/2000 APPROX db/conf/approx/approx2000.html#Hochbaum00