  Current citation practices observed in articles are very noisy, confusing,
and not standardised, making identifying the cited works problematic for
hu-mans and any reference extraction software. In this work, we want to
investigate such citation practices for referencing different types of entities
and, in particular, to understand the most used metadata in bibliographic
refer-ences. We identified 36 types of cited entities (the most cited ones were
articles, books, and proceeding papers) within the 34,140 bibliographic
references extracted from a vast set of journal articles on 27 different
subject ar-eas. The analysis of such bibliographic references, grouped by the
particular type of cited entities, enabled us to highlight the most used
metadata for de-fining bibliographic references across the subject areas.
However, we also noticed that, in some cases, bibliographic references did not
provide the essential elements to identify the work they refer to easily.
