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Internal line shifts in quasars spectra have played a more prominent role inour understanding of quasar structure and dynamics. The observed differentredshift among broad hydrogen lines is still an amazing puzzle in the study ofquasars. We have argued that the broad hydrogen lines, as well as thelow-ionization lines in quasars, are significantly contributed by the Cerenkovquasi-line emission of the fast electrons in the dense clouds/filaments/sheets($N_{\rm H}\geq 10^{14}~{\rm cm^{-3}}$); whereas this line-like radiationmechanism is invalid for producing the high ionization lines. In order toaccount for redshift difference, the Cerenkov line-like radiation mechanismcould provide a plausible resolution: it is the `Cerenkov line redshift', whichis different from line to line, causes the peculiar redshift-differences amongLy$\alpha$, H$\alpha$ and H$\beta$ lines. The different redshifts amongdifferent broad hydrogen lines could stand for an evidence to quantitativelysupport that the observed broad hydrogen lines should be blended by both thereal line emission and the Cerenkov quasi-line emission. The good fitting tothe observed redshifts of quasars confirms the existence of Cerenkov componentin the broad hydrogen lines, which indicates that, in the blended Ly$\alpha$line, the line-intensity of the Cerenkov component approximately equals that ofthe accompanying `normal line' (an approximate equipartition of intensitybetween the two components in the broad Ly$\alpha$ line). This resultillustrates the importance of the Cerenkov component in the broad lines ofquasars, which can be further confirmed by future observations.

One possible explanation for the Balmer and Lyman line shifts in quasars