Bibliographical Abbreviations are commonly used in academic writing to refer to sources that have already been cited. IBID is an abbreviation for the Latin phrase 'ibidem, ' which means 'in the same place.' It is used to refer to the same source that was previously cited. ETAL is an abbreviation for the Latin phrase 'et alii, ' which means 'and others.' It is used to refer to multiple authors of a single work. ETSEQ is an abbreviation for the Latin phrase 'et sequentes, ' which means 'and the following.' It is used to refer to multiple sources that follow a single source. OPCIT is an abbreviation for the Latin phrase 'opere citato, ' which means 'in the work cited.' It is used to refer to a source that has already been cited in the same document.