Update document.md

24spring/middle_homework/document.md

@@ -73,7 +73,7 @@ The book [1] is a great book. The article [3] is also a classic. View [2] for mo
 The book [1] is a great book. The article [3] is also a classic. View [2] for more info.
 
 References:
-[1] book: Randal E. Bryant, David R. O'Hallaron, Computer Systems: A Programmer's Perspective, Pearson, 2019
+[1] book: Randal E. Bryant, David R. O'Hallaron, Computer Systems, Addison-Wesley, 2015
 [2] webpage: PyTorch. Available at https://pytorch.org
 [3] article: Marshall Kirk McKusick, William N. Joy, Samuel J. Leffler, Robert S. Fabry, A Fast File System for UNIX, ACM Transactions on Computer Systems, 1984, 2, 3
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