Sinclair says 98% pure nitric acid is needed to make Nitroglycerin and that it is difficult to get. That is not true, concentrated Nitric Acid can be bought at ant chemical supply company, and we had bottles of it in our school chemical storeroom. It is common and easy to buy, although expensive.
Just prior to the second modern bombing, a sign of the companies in the building is shown and Amcal Petroleum Company is misspelled as Petroluem.