Fitzpatrick, Richard (July 14, 2007). "Spherical Mirrors". Electromagnetism and Optics, lectures. University of Texas at Austin. Paraxial Optics. பார்க்கப்பட்ட நாள் October 5, 2011. {{cite web}}: Unknown parameter |separator= ignored (|mode= suggested) (help)CS1 maint: extra punctuation (link)
