A Classification of Semeai with Approach Moves
  The paper analyzes liberty races (semeai) in the game of Go. A rigorous treatment of positions with approach moves but no ko revealed a class of positions not described in the literature before.   The complete presented classification is simpler and more compact than the one used so far. This was achieved through a classification by the types of liberties and the order they are to be filled instead of a classification by group status.   A principal difference to semeai without approach moves is that in the presence of approach moves and shared liberties and the absence of eyes, two different strategies are possible because the un-orthodox filling of shared liberties instead of outer liberties may be a better strategy. 
Thomas Wolf
math.CO