We discuss the results of modelling the TeV \gamma -ray spectra of two AGNs , Mkn 501 and Mkn 421 that have almost the same redshifts : z = 0.031 and z = 0.034 , respectively .
The effect of intergalactic \gamma -ray absorption is treated as an uncertainty in the measurement of the intrinsic spectrum .
Although the objects differ , we obtain satisfactory fits for both of them in a synchrotron self-Compton scenario .
Compared to previous models , our fits are characterised by higher values of the Doppler factor ( \delta \geq 50 ) and an electron injection spectrum extending to higher energies ( \gamma _ { max } \geq 1.5 \times 10 ^ { 5 } ) .
In the case of Mkn 421 , the observed difference in spectral slope in X-rays and TeV \gamma -rays between the high and low states can be explained as a variation of a single parameter — the maximum energy \gamma _ { max } mc ^ { 2 } at which electrons are injected .