"conservative" procedure: Benjamini, Y., and Y. Hochberg (1995) Controlling the false
discovery rate: a practical and powerful approach to multiple testing.
J. Roy. Statist. Soc. B, 57, 289--300.
"adaptive" procedure: Benjamini, Y., and Y. Hochberg (2000) The adaptive control
of the false discovery rate in multiple hypotheses testing with independent statistics.
J. Behav. Educ. Statist., 25, 60--83.
"bootstrap" procedure: Storey, J. D. (2002) A direct approach to false
discovery rates.
J. Roy. Statist. Soc. B., 64, 479--498.
"smoother" procedure: Storey, J. D., and R. Tibshirani (2003)
Statistical significance for genome-wide experiments.
Proc. Nat. Acad. Sci. USA, 100, 9440-9445.
"quantile" procedure: similar to smoother, except that the lower q
quantile of all eta0 computed in dependence of lambda is taken as overall estimate of eta0.