Casson–Gordon's three-family conjecture for 2-bridge ribbon knots

A 2-bridge ribbon knot is a ribbon knot that is also a 2-bridge knot. Casson and Gordon identified three families of 2-bridge ribbon knots.

Casson–Gordon's conjecture. Every 2-bridge ribbon knot is contained in one of the three families of Casson and Gordon.

The conjecture is supported computationally: it was verified for all 2-bridge knots with determinant at most $571^2$, including all such knots with crossing number at most $26$. A proof remains open in the source.