(petitioners were members of LLC that made bargain sales of open-space conservation easements to qualify charity (portion of purchase price paid by charity is gain to seller and below-market portion is contribution); IRS denied charitable contribution on basis that easements not perpetual because government agencies that funded purchase entitled to recapture upon condemnation of land and extinguishment of easement, and because appraisal not qualified and no contemporaneous written acknowledgement of gift; court disagreed with IRS – upon extinguishment taxpayers would not reap windfall and done can use its proportionate share of proceeds to advance cause of historic preservation on different property; while qualified appraisal must include statement that it was prepared for income tax purposes, appraisal report included required information either in appraisal or in summaries; contemporaneous written acknowledgement can be comprised of a series of documents).