I'm actually reading the article of Shastry "Exact solution of an S= 1/2 Heisenberg Antiferromagnetic Chain with Long-rnaged interactions", Phys. Rev. Lett. 60, 639 (1988)" The articles shows how to solve the problem of a long range-inverse squared interacting spin chain, i'm having troubles with equations 5 and 6 of the article, i tried everything but could not find the same result ! if someone knows how it goes, i'm here to discuss, Thanks !