This article discusses how the relationship among the five principal metrics of the software process can often be expresses through a Rayleigh curve.

This article discusses multiple applications based on only four measured metrics: size (function), effort, time, and defect rate. From these metrics, we can manage a project.

This article discusses the trade-off of a little more development time for a lot less effort, cost and defects in the context of the perceived need for "more software now". 

No software system of any realistic size is ever completely debugged—that is, error free

Edward Yourdon and Larry L. Constantine, 1975 1