Since you're looking to reference a manual, you may want to look into the @manual entry type. Its only required field is title, and it has the following optional fields: author, organization, address, edition, month, year, note, and key. (Any fields that are neither required nor optional will be ignored.)
You may also want to consider the entry type @unpublished; its required fields are author, title, and note, and its optional fields are month, year, and key.
If that doesn't work for you, you may want to look into BibTeX's catch-all entry type, called @misc: It has no required fields at all, and its optional fields are author, title, howpublished, month, year, note, and key.
At any rate, the @article entry type won't work for your entry because one of its required fields is (as you've already discovered) journal. If one omits the journal field from an entry of type @article, BibTeX will generate either a warning or an error message about the missing field.