Nonetheless, a core assertion in the two authors’ previous analysis of the sarin-filled rockets, also based on dimensions, has stood for months.

 That study proposed that the warheads contained a large volume, about 13.2 gallons, of sarin. The United Nations implicitly seconded that suggestion when it included a similar estimate in its own report in September.

 The assumption that the warheads contained a large volume of nerve agent also helped shape another prominent analyst’s assertion that the details of the Aug. 21 attack implicated the Syrian government.