please, I need to find 2 articles,
1. G.L EllmanA colorimetric method for determining low concentrations of mercaptans
Arch. Biochem. Biophys., 74 (1958), pp. 443-450
2.
G.L Ellman, D Courtney, V Andres, R.M FeatherstoneA new and rapid colorimetric determination of acetylcholinesterase activity
Biochem. Pharmacol., 7 (1961), pp. 88-95