In the introduction, the problem L(G) subseteq L(A) 
with G a CFG and A an NFA is mentioned to be PSPACE-complete. 
This is wrong and should be EXPTIME-complete, as proven 
in Theorem 2.1 <a href="http://hdl.handle.net/2433/82765">here</a>. 
Thanks to Pierre Ganty and Pedro Valero for pointing this out.  
The mistake does not affect the results of the paper.