Kovacs, Diane K.
The virtual reference handbook : interview and information delivery techniques for the chat and e-mail environments / Diane K. Kovacs
Facet Publishing, 2007
 Buku Referensi
Hani Kusumaningsih
Evaluasi layanan referensi e-mail Perpustakaan United Nations Information Centre Jakarta = Evaluation of e-mail reference at United Nations Information Centre Library Jakarta
Fakultas Ilmu Pengetahuan dan Budaya Universitas Indonesia, 2016
 UI - Skripsi Membership
Liu, Jia
The Evaluation of worldwide digital reference services in libraries
Chandos Publishing, 2007
 Buku Teks
Cassell, Kay Ann
Reference and information services : an introduction
Neal-Schuman, an imprint of the American Library Association, 2013
 Buku Teks
Evaluation of reference services / edited by Bill Katz and Ruth A. Fraley
Haworth Press, 1984
 Buku Referensi