1. Klaf R., Penzien D. Zh., Dynamics of Structures, (Stroyizdat, Moscow, 1979) (in Russian)
2. Lyakhovich L.S., Osobye svojstva optimal'nyh sistem i osnovnye napravlenija ih realizacii v metodah rascheta sooruzhenij [Special properties of optimal systems and the main directions of their implementation in the calculating methods of structures] (TSUAB Publ. House, Tomsk, 2009) (in Russian)