Письменний, Є. М., С. А. Рева, and О. М. Терех. “Aerodynamic Drag of Tube Bundles With the Helical-Shaped Tubes”. Eastern-European Journal of Enterprise Technologies, vol. 6, no. 8(66), Dec. 2013, pp. 31-35, doi:10.15587/1729-4061.2013.18934.