Accumulation-mode PMOS transistors on SOI are characterized by several conduction mechanisms. Measurements of the threshold voltage corresponding to each of them are presented for the first time, as well as an intuitive physical interpretation of their dependence on the front- and back-gate voltages.
Terao, A., Flandre, D., Loratamayo, E., & Vandewiele, F. (1991). Measurement of Threshold Voltages of Thin-film Accumulation-mode Pmos Soi Transistors. IEEE Electron Device Letters, 12(12), 682-684. https://doi.org/10.1109/55.116954 (Original work published 1991)