sentences:  Hoping to find another way for these S&Ls to realize their tax losses, the FHLBB promulgated a new regulation called "Memorandum R-49", under which the S&Ls would not have to show a loss on their books if they exchanged their mortgages for "substantially identical" mortgages held by other lenders.Cottage Savings made a transaction pursuant to this regulation by exchanging 90% participation interests in 252 mortgages to four other S&Ls, receiving in return 90% participation interests in 305 mortgages.All the mortgages involved in the transaction were for homes in the Greater Cincinnati region.