Analysis of a cable network with negative Gaussian curvatureLaul, Heinrich; Kulbach, ValdekRakenteiden mekaniikka = Journal of structural mechanics1974 / p. 3-18 : ill http://rmseura.tkk.fi/rmlehti/1974/nro1/RakMek_7_1_1974_1.pdf https://www.ester.ee/record=b1201967*est