  An exact expression is derived for the electron Green function in two-channel
Kondo models with one and two impurities, describing the crossover from
non-Fermi liquid (NFL) behavior at intermediate temperatures to standard Fermi
liquid (FL) physics at low temperatures. Symmetry-breaking perturbations
generically present in experiment ensure the standard low-energy FL
description, but the full crossover is wholly characteristic of the unstable
NFL state. Distinctive conductance lineshapes in quantum dot devices should
result. We exploit a connection between this crossover and one occurring in a
classical boundary Ising model to calculate real-space electron densities at
finite temperature. The single universal finite-temperature Green function is
then extracted by inverting the integral transformation relating these Friedel
oscillations to the t matrix. Excellent agreement is demonstrated between exact
results and full numerical renormalization group calculations.
