The variability of quasar light curves can be used to study the structure of quasar accretion disks. For example. continuum reverberation mapping uses delays between variability in short and long wavelength bands ( short lags) to measure the radial extent and temperature profile of the disk. Recently. https://safeersappliancers.shop/product-category/zanussi-zof35802xk-electric-built-under-double-oven-stainless-steel/