SIMBAD references

We present results of some numerical studies on the dynamical history of a large number of observed long-period comets. In our investigations we include all comets with good quality orbits. We calculated barycentric, original orbital elements for comets at a distance of 250AU from the Sun and then followed the motion of each comet (elliptic orbits only) backwards to its aphelion and then to its previous perihelion passage, including the galactic perturbations. Several previously published statistics are compared with the current sample of long-period comets having well-defined orbits. A distinction between dynamically ``new'' and ``old'' comets is proposed on the basis of their previous perihelion distance instead of the inverse of the original semimajor axis. We also demonstrated the importance of stellar perturbations and made attempts to find a correlation between past dynamics and various physical parameters of comets.