End-point singularity of the XY-paramagnetic phase boundary for the 
D 
square-lattice 
–
XY model with the single-ion anisotropy
Eur. Phys. J. B, 96 7 (2023) 96
Published online: 12 July 2023
DOI: 10.1140/epjb/s10051-023-00566-3