"Regarding Jones' theory that nanothermite was used to bring down the towers, and the assertion that thermite and nanothermite composites were found in the dust and debris were found following the collapse of the three buildings, which was concluded to be proof that explosives brought down the buildings, Brent Blanchard, author of "A History of Explosive Demolition in America", states that questions about the viability of Jones' theories remain unanswered, such as the fact that no demolition personnel noticed any telltale signs of thermite during the eight months of debris removal following the towers' collapse.Blanchard also stated that a verifiable chain of possession needs to be established for the tested beams, which did not occur with the beams Jones tested, raising questions of whether the metal pieces tested could have been cut away from the debris pile with acetylene torches, shears, or other potentially contaminated equipment while on site, or exposed to trace amounts of thermite or other compounds while being handled, while in storage, or while being transferred from Ground Zero to memorial sites.