USC Library physical resources are shelved in alphabetical order by Library of Congress Classification (LCC) call number. The call number is located on the spine or front cover of the item and relates to the subject matter covered by the resource. When you find one item on the shelf about your desired topic, browse the items on the shelf around it as they will most likely contain content relevant to your research.
The first line is read in alphabetical order. The letter(s) relates to the broad subject area e.g. GB indicates that book is about physical geography.
The second line is read as a whole number. The number relates to a more specific subject area e.g. 5011.89 indicates this book is about natural disasters.
The third line is read in alphabetical order, then as a decimal number. The letter and number indicates the author's surname e.g. Davidson.
The fourth line is read as a whole number and indicates the year of publication e.g. the year 2020.