Holford's GL reference list is derived from research published in the American Journal of Clinical Nutrition, Vol 76(1) (2002) pp 5 - 56. See here for more info. From this webpage, you're able to download the whole article which includes the INTERNATIONAL TABLE OF GLYCEMIC INDEX AND LOAD. However, Holford's book simplifies this table and picks out the common foods that we eat and also filters out many of the ready-made processed foods which I don't eat anyway.
This site is awesome. Also by our hero Patrick Holford. You can type in any ingredient and it will give you the GL of the food and recommended serving sizes. Very helpful!
