@article {8325,
	title = {Two-photon-excitation fluorescence imaging of three-dimensional calcium-ion activity},
	journal = {Applied Optics},
	year = {1994},
	pages = {662-669},
	author = {David W. Piston and Mark S. Kirby and Heping Cheng and W.J. Lederer and Watt W. Webb}
}
