Very briefly, 'cos I'm in a rush:
The speed range below L/DMAX in a jet is the speed unstable regime. That above it is the speed stable regime. In the speed stable regime, power is added to increase speed, as normal. In the speed unstable regime, however, power has to be added to maintain a slower speed, and there is less of a tendency to return to trim speed anyway, so control movements must be more precise.
It's not all you need but it's a start.....