^{page no 55 note *} Vol. 34 (1950), note 2144, pp. 129–133.

^{page no 56 note *} We use here the convention that θ is to be measured in the positive (anti-clock¬wise) sense about A from AB (though the line through A may well lie outside the triangle, and θ need not be restricted to lie in the range 0≤θ<2π), and similarly for φ, ψ. The senses of the lines are, of course, irrelevant, since (2) is unaltered if we increase any of the angles θ, φ, ψ by π (or, indeed, by any multiple of π), while the condition of concurrency is also unaffected.