My previous mail was made without any reference material.
Tonight I looked up the relevant position in Marin's book:

The postion in question after the 13th move is in facted given in a footnote in marin's book. Conclusions:
1. I badly garbled the name of Spasski;s opponent:
Maia Chiburdanidze- Spasski, Monte Carlo 1994.
Marin however has a good recommendation against 14.a4:
14...Rab8 apparently equalizing.
Nevertheless the game is perfect study material to show white's
chances. Imo Maia missed a good chance to reach a near winning
position.

2. Marin takes  13.b3, Ne8 14.Nbd2 as his only other line in the footnote, advocating a passive defence in  Rubinstein style
giving a game that ended in a short draw, providing a single line without alternive moves. The implied verdict - easy equality - is not borne out by the position in question, which has been reached by transposition.
Especially as imo 17.h3 is indead not the strongest move, but
17.Ng3 (a move played by M.Adams in the Moskou 2007 blitz tournament, but allready played in 1997)

3. Recent mastergames seem to preferr 13....Nb7 over 13....Ne8.

4. Studying the commented game of the chapter (with the line 13.Nbd2) provides the idea of playing Nh5-Bf6-Nf4. As Marin explains this makes use of the relative undefended b2/c3 squares in the position.

5. This idea has indeed put into practice:
starting off with either 13...g6 or 13....Rfe8. The relevant variations
(where transpositions are possible) 

13...g6 14.Bh6,Rfe8 15.Nbd2,Nh5 16.Nf1,Bf6 (or)
13...Rfe8 14.Nbd2,g6 15.Nf1,Nh5 16.Bh6,Bf6! 

and black can follow up with 17...Bg7 securing his kingside.
Stevic-Blagojevic, Croatia, 2003 (both players rated 2500+) where
black apparantly reached a satisfactory position from the opening.

My conclusions on the chapter Worall-attack are:
I. Marin provides an excellent commented game, which arms the reader with valuable advice how to handle this kind position.
II. The theoretical section provides some good material and suggestions as well.
III. The theoretical section might have been researched somewhat better, although I comprehend Marin's choice to provide variations
that are strongly related to the main Rubinstein strategy.

It's finally time to get back to some real serious chess discussion on this forum!

In Mihail Marin's book, A Spanish Repertoire for Black, against the main line of the Worrall Attack he recommends 1 e4 e5 2 Nf3 Nc6 3 Bb5 a6 4 Ba4 Nf6 5 Qe2 b5 6 Bb3 Be7 7 0-0 0-0 8 c3 d6 9 Rd1 Na5 10 Bc2 c5 11 d4 Qc7 12 d5 Bd7 13 b3 Ne8 14 Nbd2 g6 15.Nf1 Ng7 16.Bh6 f6 and now only covers what to do if White plays 17 h3. In Andrew Greet's book, Play the Ruy Lopez, instead of 17 h3 he recommends 17 a4 or 17 N3d2. 

I have three questions about this line:

1. Is 13...Ne8 Black's best move?

2. Is 14 Nbd2 g6 15.Nf1 Ng7 16.Bh6 f6 the best follow up to 13...Ne8 for Black?

3. How should Black meet 17 a4 and 17 N3d2?