“…For solutions of boundary value problems which satisfy appropriate conditions, Rf (θ) can be proven to exist for θ ∈ [−α, α] \ J, where J is a countable subset of (−α, α) (e.g. [3,4,8,10,11,12,13]). We know of no examples in which J = ∅ and we ask if J = ∅ always holds; this is related to the existence of cusp solutions.…”