From the example above, it is obvious that the advantage of
author number over a simple letter system is the power to maintain
an accurate alphabetical order in the sequence. An obvious
disadvantage is the fact that we need to purchase and use the tool
to do so. Another disadvantage relates to the user un-friendliness
of the call number - but this is something that can be endlessly
argued about. Those disliking author numbers argue that when used
alongside a class mark, an author number may appear visually less
distinct and thus may make re-shelving that little slower. But this
objection entirely depends on the type of classification notation
used and of the design of the book label2