Jones has not explained how the amount of explosive needed to bring down the buildings could have been positioned in the two buildings without drawing attention, but mentioned efforts to research the buildings' maintenance activity in the weeks prior to the event. Federal investigators at the National Institute of Standards and Technology state that enormous quantities of thermite would have to be applied to the structural columns to damage them, but Jones disputed this, saying that he and others were investigating "superthermite". Brent Blanchard, author of "A History of Explosive Demolition in America", who corresponded with Jones, 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 said 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.