How do I locate a book?

All books are shelved according to a system made up a combination of numbers and letters. The numbers represent a topic whereas the letters are identical to the first three letters of the author surname or the book title.

First use the numbers to locate the shelf that holds the books covering the topic, now use the letters, which are sorted alphabetically.

Numbers range from 001 to 939, starting on the 2nd floor by the window, making their way through the library to the basement.

Examples:
001.81 rei
658.850 ben

Please do not hesitate to ask a member of staff for directions.