Παραπομπή σε μορφή APA (7η εκδ.)

Essen University Library & Helal, A. H. (1991). Information technology and library management: 13th international Essen Symposium 22 October- 25 October 1990. Universitaetsbibliothek Essen.

Παραπομπή σε μορφή Chicago (17η εκδ.)

Essen University Library και Ahmed H. Helal. Information Technology and Library Management: 13th International Essen Symposium 22 October- 25 October 1990. Essen: Universitaetsbibliothek Essen, 1991.

Παραπομπή σε μορφή MLA (8th εκδ.)

Essen University Library και Ahmed H. Helal. Information Technology and Library Management: 13th International Essen Symposium 22 October- 25 October 1990. Universitaetsbibliothek Essen, 1991.