John A. Townsend (Houston; Google Scholar), The Tax Contribution To Deference And APA § 706:

The tax authorities supporting APA to include deference are compelling. These tax authorities have been marginalized in the discussion. The law at the time of the APA in 1946 was settled to include deference when (i) the statute was ambiguous and (ii) the agency interpretation within the scope of the ambiguity was reasonable. That was Chevron deference before Chevron. That alone would support interpreting APA § 706 to include deference. But, there is more. 

Section 706 states the standard of review for interpretations “not in accordance with law” which the Supreme Court interpreted in Dobson, a 1943 tax case, to mean review with deference rather than review de novo.