Walter Sneader based his claims that Eichengrün both invented the process for synthesizing aspirin and oversaw its clinical testing on old and newly released archived materials, including letters, patents, and lab work. He found that Hoffman was not credited with inventing the process for synthesizing Aspirin in any documents prior to 1934, 37 years after its initial synthesis. Further he found reason to doubt the footnote's credibility, not just for being published during the "Aryanization" period of Nazi Germany, but for its inaccurate claims about the testing of salicylic acid derivates other than acetyl ester. The vague reference did not specify which derivatives were tested, but claimed they had been discovered earlier but had been synthesized for "other purposes". No indication was given of what the others were, but in 1899 Heinrich Dreser, head of the experimental pharmacology laboratory at Elberfeld, named them in a publication as propionyl, butyryl, valeryl, and benzoyl salicylic acids. He further alluded to these derivatives in 1907 and again in 1918. However, the assertion that these salicylic acid derivates had been synthesized for non-therapeutic reasons is demonstrably false. Hoffmann's colleague Otto Bonhoeffer (who also worked under Eichengrün) had been awarded a US and UK patent in 1900 for several of these compounds. The patents indicate that the derivatives were prepared for the exact purpose of finding a salicylic acid derivative with therapeutic value. Sneader concluded that because of this error the 1934 footnote is unreliable.