dx.doi.org/10.1088/0950-7671/42/6/307
J. Sci. Instrum.

van Deenen, P. J, Matitti, T, & Vermeer, A. (1965). A transistor amplifier for registration of the low current part of a Langmuir probe characteristic. J. Sci. Instrum., 42. doi:10.1088/0950-7671/42/6/307