Jusqu-a Airmail Markings- A Study Ian Mcqueen -

Some "Jusqu’à" points (like obscure colonial outposts) were only active for weeks, making their markings highly prized. Conclusion Ian McQueen’s Jusqu’à Airmail Markings

McQueen provides detailed listings for over 150 distinct markings, noting periods of use, rarity, and known covers. Jusqu-a Airmail Markings- A Study Ian McQueen

Ian McQueen is a renowned philatelic author who specialized in these often-overlooked auxiliary markings. His book, "Jusqu'à Airmail Markings: A Study," noting periods of use