Download pcmcia-source, by typing
apt-get install pcmcia-source  | 
/usr/src  | 
pcmcia-cs.tar.gz  | 
You now need to gunzip the file by
gunzip pcmcia-cs.tar.gz  | 
tar xvf pcmcia-cs.tar  | 
You should see pcmcia-source unpacked into the directory
/usr/src/modules/pcmcia-cs  |