Langer, H., Langer, M. and Sasvári, Z. (2004) “Continuations of Hermitian indefinite functions and corresponding canonical systems: an example”, Methods of Functional Analysis and Topology, 10(1), pp. 39–53. Available at: https://zen.imath.kiev.ua/index.php/mfat/article/view/230 (Accessed: 17 December 2025).