Brooks's Law: Adding manpower to a late software project makes it later.
In most projects, the first system built is barely usable. It may be too slow, too big, awkward to use, or all three. There is no alternative but to start again, smarting but smarter, and build a redesigned version in which these problems are solved.
The bearing of a child takes nine months, no matter how many women are assigned.
The essential prerequisite for building an expert system is to have an expert.
Thinkers are rare; doers are rarer; and thinker-doers are rarest.
When schedule slippage is recognized, the natural (and traditional) response is to add manpower. Like dousing a fire with gasoline, this makes matters worse, much worse.