Burge, James H. (1993). Null test for null correctors: error analysis(PDF). SPIE's 1993 International Symposium on Optics, Imaging, and Instrumentation. International Society for Optics and Photonics. pp. 86–97. "The hologram is designed and fabricated independently from the null corrector, so agreement between the two indicates a high probability that both are correct."
Lew Allen (Chairman) (1990). "The Hubble Space Telescope Optical Systems Failure Report"(PDF). NASA Technical Report NASA-TM-103443. The definitive report on the error in the Hubble mirror, traced to an error in the construction of the reflective null corrector.