1. Every planar map is four colorable. Part I: Discharging
2. Every planar map is four colorable. Part II: Reducibility
3. and Stars and bunches in planar graphs. Part I: Triangulations. CDAM Research Report Series 2002-04 (2002). Original Russian version. In: Diskretn Anal Issled Oper Ser 1 8, no. 2 ( 2001), 15-39.
4. and Stars and bunches in planar graphs. Part II: General planar graphs and colourings. CDAM Research Report Series 2002-05 (2002). Original Russian version. In: Diskretn Anal Issled Oper Ser 1 8, no. 4 ( 2001), 9-33.