Helen B. Sawyer A Bibliography of Individual Globular Clusters

A Bibliography of Globular Clusters 393
III. Instructions for Use of Bibliography
All references to individual globular clusters are listed in Section
A where the clusters are arranged by NGC number, with Messier's
number indicated in parenthesis. The Right Ascension and Dec-
clination are for 1950; the galactic coordinates are for 1900.
Under each cluster are listed by date, author and title all prin-
cipal papers on that cluster. Many important references to indi-
vidual clusters are lost in works on another cluster or subject; every
attempt has been made to include these stray bits of information.
Numerous papers intercompare clusters, and these are listed under
each cluster so compared.
Papers which involve several or more clusters are usually listed
under each cluster concerned by date and author only. The complete
reference list for these items will be found in Section B. There
was no iron-clad rule as to whether papers mentioning a few clusters
should be listed by title under each cluster, but in general Section B
is a list of catalogues and works providing observational data on
many clusters. Since the New General Catalogue number by
Dreyer, 1888, is used for each cluster, there is. no additional
reference to this catalogue by individual cluster.
The first date and name reference under NGC 104, 47 Tucanae,
is 1755 Lacaille. If the reader will turn to Section B, he can read
the title of the paper as well as the printed source. For some of the
early catalogues, notably those of Lacaille, the Herschels and
Dunlop, the catalogue number of the object follows the name of
the author. When photographs or drawings accompany the paper
this is usually, but not always, indicated. Certain clusters, such as
Messier 13, have had too main- photographs published for all to be
included, but I have attempted to indicate sources where photo-
graphs of the less well-known clusters can be found.
Many of the longer and more important references in Section B
have been indexed with lettered sub-divisions. Early in the work
it appeared that to list a cluster as being included in a given refer-
ence was not always enough. For example, a reference may contain
one list of clusters which the writer of the paper considered globular,
and another list considered as non-globular. Simply to index both
lists in the same way would be quite misleading. For these papers,
then, I have made as many lettered subdivisions as seemed neces-
sary to serve as an information guide to the material contained