Setting the the BibTeX labels

In the 'Label Pattern' tab in Preferences, one can set the fields used in auto generation of BibTex labels. The pattern can be set for each of the standard entry types. The pattern is of the form: [field1]separator[field2]separator[field3]..., where 'field#' is one of the (required) fields of a given entry type. The square brackets are quite important. They're used to recognize which part of the string is a field, and which part is a separator. This way one is not restricted to use underscore as a separator. The label can contain the first or last page by using the fields firstpage and lastpage (non BibTeX fields). The default is [author]_[year], and since this is not a unique key, it's made unique by adding one of the letters a-z until a unique key is found, so the labels might look like:
Yared_1998 Yared_1998a Yared_1998b