  Via projection operator technology, we restrict our discussion of Double
Quantum Dots system in subspaces of fixed electron population. When an incident
electron tries to pass through the dots, we find transmission peaks occur, if
the system energy scans through eigen-levels in one-more-electron higher
subspace of the dots. Also, we find some selection rules for this resonant
transmission. We attribute some of these rules to the differences between
many-electron bonding states and anti-bonding states.
