1) 

Ash, J. Marshall; Erdos, P.; Rubel, L. A. 
Very slowly varying functions.   Aequationes Math. 10 (1974), 1--9. 


2)
Ash, J. M.; Ash, P. F.; Fefferman, C. L.; Jones, R. L.
Singular integral operators with complex homogeneity.    Studia Math. 65 (1979), no. 1, 31--50. 

3)
Fefferman, C.; de la Llave, R. 
Relativistic stability of matter. I. Rev. Mat. Iberoamericana 2 (1986), no. 1-2, 119--213. 


4)  
Falcolini, C,  de la Llave, R.  
A rigorous partial justification of Greene's criterion. J. Statist. Phys. 67 (1992), no. 3-4, 609--643.  
 
5) 
Berretti, A.; Celletti, A.; Chierchia, L.; Falcolini, C. 

"Natural boundaries for area-preserving twist maps". 

J. Statist. Phys. 66 (1992), no.  5-6, 1613--1630


6) 
Chierchia, Luigi; Perfetti, Paolo 

"Second order Hamiltonian equations on $T\sp \infty$ and almost-periodic solutions". 

J. Differential Equations 116 (1995), no. 1, 
172--201.