4Hegarty M., Kozhevnikov M. Types of visual.7 spatial representations and mathematical problem solving.-Journal of Educational Psychology, 1999,91 (4) : 684 - 689.
5Novick L R, Hmelo C E, Transferring symbolic representations across nonisomorphic problems. Journal of Experimental Psychology: Learning, Memory & cognition, 1994,20 (6) : 1296 - 1321.
6Novick L R, Hurley S M, Francis M. Evidence for abstract, schematic knowledge of three spatial di&gram representations. Memory&cognition, 1999,27(2) :288 - 308.