"According to the formula, the minimal covering weight could be achieved only if the construction had no s and if the distance between es was equal to the distance between the missing purlins. The answer to this riddle was the spatial lattice structure, where trusses and purlins were the same, and the distances between trusses and purlins were equal. In 1895 Shukhov obtained a patent for the invention. The new structures were first presented to the general public at the All-Russian Industrial Art Exhibition in Nizhniy Novgorod in 1896... where Shukhov designed a number of objects using three types of lattice structure: suspension, vaulted and rigid spatial shell."