The CTEQ6 family of PDFs is superseded by newer, more complete, CT10 PDF sets. 
CTEQ6 parton distribution functions are publicly available as a part of the LHAPDF Fortran library 
Here you can download a standalone Fortran interface and demonstration program, as well as the tables with interpolated PDF values for the latest generalpurpose set (CTEQ6.6M and 44 eigenvector sets for computation of PDF uncertainties) and other CTEQ6.XX sets. 
An alternative interface for simultaneous interpolation of several CTEQ PDF tables has been developed by Zoltan Nagy. It is written in C and can be linked to C/C++/Fortran modules using gcc and other compilers. 
PDF
set 
Description 
Authors
or main contact 
References 
Date 
Tables 
Additional
resources 
CTEQ6.6AS  6.6 series with a varied strong coupling alpha_s (M_{Z})=0.116, 0.117, 0.119, 0.120 for n = 0...3  H.L.
Lai 
arXiv:1004.4624 
03/2010  ctq66as.pds.zip  
CTEQ6.6C  6.6 intrinsic charm series (n = 0...3)  J.
Pumplin 
arXiv:0802.0007  02/2008  ctq66c.pds.zip  
CTEQ6.6 
generalpurpose
CTEQ6.6M
+
44
eigenvector sets 
P.
Nadolsky
et al. 
arXiv:0802.0007 
02/2008 
ctq66m.pds.zip  Extra figures, cross sections 
CTEQ6.5.snn 
6.5
symmetric
(nn=+0...+4)
and asymmetric (nn=2...0) strangeness series 
H.L. Lai et. al.  hepph/0702268  02/2007 
ctq65s.pds.zip  
CTEQ6.5.cn

6.5 intrinsic charm series (n = 0...6)  J. Pumplin et.al  hepph/0701220  01/2007 
ctq65c.pds.zip  
CTEQ6.5 
generalpurpose
CTEQ6.5M
+
40
eigenvector sets 
W.K. Tung et.al.  hepph/0611254  12/2006 
ctq65m.pds.zip  
CTEQ6AB  Alphaseries (for two definitions of Alpha)  J.
Pumplin
et al. 
hepph/0512167  12/2005 
LHAPDF  
CTEQ6.1 
generalpurpose CTEQ6.1M + 40 eigenvector sets  D.
Stump
et al. 
hepph/0303013  03/2003 
cteq61.xx.zip  
CTEQ6HQ,
CTEQ6S 
CTEQ6
series
in
the generalmass
scheme (HQ) and for alternative strangeness parametrizations (S) 
S.
Kretzer
et al. F. Olness et al. 
hepph/0307022 hepph/0312323 
07/2003 12/2003 
cteq6.pds.zip  
CTEQ6 
generalpurpose
CTEQ6M
+
40
eigenvector sets CTEQ6M, CTEQ6D, CTEQ6L, CTEQ6L1 
J.
Pumplin
et al. 
hepph/0201195  01/2002 
cteq6m.xx.zip cteq6std.zip 
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Foundation under Grant No. PHY0855561.