Please check the following carefully:

• have you made any typing errors?
• have you decided what you want to search for and set the search field correctly? "title keyword" lets you search for relevant and significant terms contained in the title. "exact title" assumes you know exactly how the title begins (including any initial articles). You can use "Schlagwort (dt.)" (German subject terms) to search for particular subjects; we recommend you also use the "Index", which lists all the main subject terms assigned by the Library.
• are you looking for books before 1944 or published between 1851 and 1943 which may not yet be in the OPACplus?
• are you looking for periodical articles? Please note that you will only find periodical titles in the OPACplus.
• limit your search to a few well-chosen terms. Remember - less can often mean more!
• if you have too many hits, limit your search. For example, if you only want periodicals titles containing a certain term, but not books, then set the additional search option "Publication Type" on "Journal".