Campus, A., Matey, G., & Legoupil, H. (1984). Determination of the Cleanliness of High-voltage Insulation Compounds By a Laser Inspection Technique. IEEE Transactions on Power Apparatus and Systems, 103(10), 2812-2815. https://doi.org/10.1109/TPAS.1984.318278 (Original work published 1984)