L6a3 Further Notes and Views

Ruberman, Cochran, Melvin, Akbulut, Gompf, Kirby [1]

Rich Schwartz' "72" [2]

Triangle interlaced with a circle, a traditional symbol of the Christian Trinity (less used in recent centuries)

An architectural trefoil (the outline of three overlapping circles) interlaced with an equilateral triangle, another old Christian Trinitarian symbol.