Tweedie, Charles: "Inequality theorem regarding the lines joining corresponding vertices of two equilateral, or directly similar, triangles", {Part 1 of 2 (Part 2: 12 February 1904)}
Picken, D K: "On the fractional infinite series for cosec x, sec x, cot x and tan x"
Picken, D K: "Note on the method of finding the particular integral of the differential equation f (D)y =
akxk"