The papers, as cited by Elson in Webb's obituary, are:
Magde D, Elson EL, Webb WW (1972). "Thermodynamic fluctuations in a reacting system—Measurement by fluorescence correlation spectroscopy". Phys. Rev. Lett. 29 (11): 705–708. Bibcode:1972PhRvL..29..705M. doi:10.1103/PhysRevLett.29.705.
Denk, W., Strickler, J. H., Webb, W. W. (1990). Two-photon laser scanning fluorescence microscopy. Science, 248(4951). https://doi.org/10.1126/science.2321027
So, P.T.C., Kim, K.H., Buehler, C., Masters, B.R., Hsu, L., Dong, CY. (2001). Basic Principles of Multiphoton Excitation Microscopy. In: Periasamy, A. (eds) Methods in Cellular Imaging. Methods in Physiology. Springer, New York, NY. https://doi.org/10.1007/978-1-4614-7513-2_9
Zipfel W, Xu C, Elson E, Maiti S (March 2021). "Memorial Viewpoint for Watt W. Webb: An Experimentalist's Experimentalist". J Phys Chem B. 125 (11): 2793–2795. doi:10.1021/acs.jpcb.1c01045. PMID33622036. S2CID232037668.
The papers, as cited by Elson in Webb's obituary, are:
Magde D, Elson EL, Webb WW (1972). "Thermodynamic fluctuations in a reacting system—Measurement by fluorescence correlation spectroscopy". Phys. Rev. Lett. 29 (11): 705–708. Bibcode:1972PhRvL..29..705M. doi:10.1103/PhysRevLett.29.705.
Zipfel W, Xu C, Elson E, Maiti S (March 2021). "Memorial Viewpoint for Watt W. Webb: An Experimentalist's Experimentalist". J Phys Chem B. 125 (11): 2793–2795. doi:10.1021/acs.jpcb.1c01045. PMID33622036. S2CID232037668.
Zipfel W, Xu C, Elson E, Maiti S (March 2021). "Memorial Viewpoint for Watt W. Webb: An Experimentalist's Experimentalist". J Phys Chem B. 125 (11): 2793–2795. doi:10.1021/acs.jpcb.1c01045. PMID33622036. S2CID232037668.