1. Langmuir, I. and H. Mott-Smith, Jr.: Studies of Gas Discharges at Low Pressures, Gen. Elec. Rev. 27:449, 538, 616, 762, 810, 1924. (five papers).
2. Langmuir, I. and H. Mott-Smith, Jr.:The Theory of Probes in Gaseous Discharges, Phys. Rev. 28: 727, 1926.
3. Despite their age, those papers have kept most of their interest. The second one is highly theoretical.
4. Allen et al.: The Collection of Positive Ions by a Probe Immersed in a Plasma, Proc. Phys. Soc. (London) 70B: 297, 1957.
5. Bohm, D., E. H. S. Burhop and H. S. W. Massey: The Use of Probes for Plasma Exploration in Strong Magnetic Fields, In Characteristics of Electrical Discharges in Magnetic Fields, eds. Gutherie and Wakerling, New York: McGraw-Hill, 1947.