1 S. K. Vsekhsvyatskii, 1964. "Physical Characteristics of Comets", trans. Israel Program for Scientific Translations, NASA TT F-80 / OTS 62-11031. The original publication ran approximately 600 pages and included a table titled "Catalogue of Absolute Magnitudes" which comprises the data in this data set; plus a second, far more extensive table called "Observations and Physical Characteristics". The second table was not included in the English translation used to prepare these files. There are no head diameters or tail lengths listed in the Absolute Magnitude table; thus no record from this reference is included in the "pccds.tab" file. The description of the table values in this reference indicates that the quality of the H10 values is given on the following scale: 1 possible error of up to 1 magnitude 2 error does not exceed 0.4 - 0.6 magnitudes 3 error within 0.1 - 0.2 magnitudes 2 S. K. Vsekhsvyatskii, 1963. "Absolute Magnitudes of 1954-1960 Comets", Soviet Astronomy - AJ [in English], Vol. 6, 849-853. This article continues the compilation begun in the 1964 book. Updated parameters are included for those comets from the first publication which were further observed, in addition to the new comets listed. Head diameters and tail lengths are included in this and all subsequent publications. H10 quality codes and tail visibility indicators are also included in this article. The description of the table values in this reference indicates that the quality of the H10 values is given on the following scale: 1 possible error of up to 1 magnitude 2 error does not exceed 0.4 magnitudes 3 error does not exceed 0.1 - 0.2 magnitudes 3 S. K. Vsekhsvyatskii, 1967. "Physical Characteristics of Comets Observed During 1961-1965", Soviet Astronomy - AJ [in English], Vol. 10, 1034-41. H10 quality codes are included, but from this point forward none of the publications include the tail visibility flags. Included in the article are notes concerning the individual observations and objects. The description of the table values in this reference indicates that the quality of the H10 values is given on the following scale: 1 possible error of order 1 magnitude 2 error does not exceed 0.3 - 0.4 magnitudes 3 error is less than 0.1 magnitudes 4 S. K. Vsekhsvyatskii and Il'ichishina, N. I., 1971. "Absolute Magnitudes of Comets, 1965-1969", Soviet Astronomy - AJ [in English], Vol. 15, 310-313. This article was completely superceded by the next publication. There were no comets listed here which were not also listed in the 1974 reference. Since the present data set was compiled only from the latest available data for each object, there are no records originating from the table in this article. It is included here for completeness, and because it is the last of the series available in an English translation. (The notes regarding objects and observations found in most of the other articles are not present here.) 5 S. K. Vsekhsvyatskii and Il'ichishina, N. I., 1974. "Fizicheski Kharakteristiki Komet, 1965-1970gg" [in Russian] (Moskva: Izdatel'stva Nauka). Neither H10 quality codes nor tail visibility indicators are included in this publication, nor are tail type indicators. There are extensive notes included on the various observations contributing to the collection. 6 S. K. Vsekhsvyatskii, 1979. "Fizicheskie Kharakteristiki Komet 1971-1975gg" [in Russian] (Kiev: Naukova Dumka). This publication includes neither H10 quality codes or tail visibility indicators, but it does include the tail type flags which have been incorporated into the "pccds.tab" file. Also included are extensive notes about the individual observations.