Douglas, N. G. (1977). Threshold fluid logic: An M.E. project report submitted by N.G. Douglas of the Department of Mechanical Engineering, University of Canterbury. University of Canterbury.

Douglas, Neil Gordon. Threshold Fluid Logic: An M.E. Project Report Submitted by N.G. Douglas of the Department of Mechanical Engineering, University of Canterbury. Christchurch: University of Canterbury, 1977.

Douglas, Neil Gordon. Threshold Fluid Logic: An M.E. Project Report Submitted by N.G. Douglas of the Department of Mechanical Engineering, University of Canterbury. University of Canterbury, 1977.