@article{ZNSL_1995_224_a2,
     author = {I. V. Abarenkov},
     title = {Perturbation theory for the ground singlet state of the {Heisenberg} spin~1/2 antiferromagnetic chain},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {14--35},
     publisher = {mathdoc},
     volume = {224},
     year = {1995},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_1995_224_a2/}
}