root@web1:~# aptitude why linux-headers-3.13.0-115
i   python-keyring                      Suggests python-kde4                        
p   python-kde4                         Depends  phonon                             
p   phonon                              Suggests phonon-backend-vlc                 
p   phonon-backend-vlc                  Depends  vlc-nox                            
p   vlc-nox                             Depends  libcrystalhd3                      
p   libcrystalhd3                       Suggests firmware-crystalhd                 
p   firmware-crystalhd                  Suggests linux-image                        
p   linux-image-3.13.0-115-lowlatency   Provides linux-image                        
p   linux-image-3.13.0-115-lowlatency   Suggests linux-headers-3.13.0-115-lowlatency
p   linux-headers-3.13.0-115-lowlatency Depends  linux-headers-3.13.0-115