Tips
Call numbers are organized by subject. When you find your book on the shelf, take a minute to look around to see if there are others that may be of interest.
Library of Congress Call Numbers
Most of the Library uses the Library of Congress Classification System.
| PS3551 | The numbers following the letter(s) are read as a whole number (three thousand five hundred and fifty-one). PS3551 would come before PS3650. |
| .5 | If there are additional numbers immediately after the whole number, you should treat them as a decimal.PS3551.5 would come between PS3551 and PS3552. |
| .N257 U53 |
For the next part of the call number, go to the letter(s) and then treat the number(s) as a decimal. .N257 U53 would come between .N257 U450 and .N257 U6. |
| 1999 | The final number, if included, is the year of publication.This book was published in 1999. |
Dewey Decimal Call Numbers
Some of the John Crerar Library's collections on the Lower Level are shelved by the Dewey Decimal Classification System.
| 630.51 | The number in front of the decimal is read as a whole number (six hundred and thirty), then treat the rest as a decimal. 630.4 would come between 630.31 and 630.52. |
| P884 | For the final number, go to the letter first and then read the rest as a whole number. P884 would come between P883 and P885. |
Harvard Yenching Call Numbers
Some materials from the Library's East Asian Collection are shelved by the Harvard Yenching system.
| 8911 |
The numbers are read as a whole number (eight thousand nine-hundred and eleven). 8911 would come before 8950. |
| .5 | If there are additional numbers immediately after the whole number, you should treat them as a decimal. 8911.5 would come between 8911 and 8912. |
| 4426 | The next number is also read as a whole number. |
Reading Other Call Numbers
SuDoc
Some government publications at D'Angelo are shelved by the Superintendent of Documents Classification System (SuDocs). Boston College has a nice guide to reading SuDocs numbers.
Benyon K and LC K (XXK)
The Library uses two classification systems for legal materials, Benyon K and the Library of Congress K classification. To distinguish the two K call numbers, we precede LC call number with XX (example, XXKF 1000). Both call numbers are read just as you would any other Library of Congress call numbers.
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