diff --git a/README.md b/README.md
index 7c5ddb9..ed351dd 100644
--- a/README.md
+++ b/README.md
@@ -2,7 +2,7 @@ This repo is the home of an effort to turn the orignal tutorial covering [xlrd][
 
 It is currently stalled and likely always will be. In the meantime, here's a link to a PDF rendering of the original Open Office document: 
 
-http://www.simplistix.co.uk/presentations/python-excel.pdf
+https://github.com/python-excel/tutorial/raw/master/python-excel.pdf
 
 [1]: https://github.com/python-excel/xlrd
 [2]: https://github.com/python-excel/xlwt
diff --git a/python-excel.pdf b/python-excel.pdf
new file mode 100644
index 0000000..c5c0333
Binary files /dev/null and b/python-excel.pdf differ
diff --git a/students/xlrd/dates.py b/students/xlrd/dates.py
index ab8f8c8..0007e6d 100644
--- a/students/xlrd/dates.py
+++ b/students/xlrd/dates.py
@@ -3,6 +3,7 @@
 
 book = open_workbook('types.xls')
 sheet = book.sheet_by_index(0)
+import math
 
 date_value = xldate_as_tuple(sheet.cell(3,2).value,book.datemode)
 print datetime(*date_value),date(*date_value[:3])