Writing the report / assignment

Do not confuse the publisher and the printer.
Do not include unnecessary and unwieldy parts of the publisher's name, such as & co., ltd., press, & associates etc.
Some examples:

Phaidon (NOT Phaidon Press Limited)
Longman
Penguin
HAUM
Methuen
Nasou
Van Nostrand
McGraw-Hill
Routledge & Kegan Paul (note the use of the ampersand "&")
If no publisher can be found, use s.n. (sine nomine). [Use italics for the Harvard method] [For the APA method, no italics, e.g. s.n. (sine nomine)].
NB. University presses: note that there is a difference between a work published by Oxford University Press or by Oxford University.
NB. Publishers are not always commercial undertakings. They may be government or corporate bodies (e.g. UNESCO, World Health Organisation, Organisation for African Unity, African National Congress, etc.).

The elements required to compile a bibliography