Donner's Puzzle

(1) Djaja - White to play and draw Donner book 1.Nf5+ Kd8 2.Ra8+ [2.Nxd4 a2 3.Rb7 (3.Nc2 Rb2 and Black wins.) 3...a1Q 4.Rxb6 Qxd4 5.a7 ] 2...Kxd7 3.a7 Ra4 4.Rg8 Rba6 5.Nh6!! and now White has perpetual check along the g-file! Draw. 1/2-1/2