Update bzip2 download link

README.rst

@@ -43,17 +43,19 @@ to 2.7 and don't require anything extra.
 
 For ``openssl``, step 5 will be more complicated :)
 
+For ``libffi``, before step 5 each include/<arch>/fficonfig.h and 
+include/<arch>/ffi.h must be generated by running CPython's PCBuild/configure_headers.bat.
 
 Download links
 --------------
 
 - ``sqlite``: https://www.sqlite.org/download.html
-- ``bzip2``: http://www.bzip.org/downloads.html
+- ``bzip2``: https://www.sourceware.org/bzip2/downloads.html
 - ``xz``: https://tukaani.org/xz/
 - ``zlib``: https://zlib.net/
 - ``tcl``/``tk``: https://tcl.tk/software/tcltk/download.html
 - ``openssl``: https://www.openssl.org/source/
-
+- ``libffi`` : https://github.com/libffi/libffi
 
 Tagging the commit
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