In Appendix B we present plots of V(1,1,0) vs. r for the 138 comets for which data is available (an example is presented in Fig. 2). The vertical lines indicate the perihelion and aphelion distances. Since the comet may have changed these two values during the observed period, we choose the minimum perihelion and maximum aphelion distance in that period of time. Different symbols are assigned to selected observers and observational categories as discussed in Sect. 3.2. The observations are classified using the following groups:
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