[经] back to back credit of credit

shū chū wèi xiān de duì kāi xìn yòng zhèng ㄕㄨ ㄔㄨ ㄨㄟˋ ㄒㄧㄢ ㄉㄜ˙ ㄉㄨㄟˋ ㄎㄞ ㄒㄧㄣˋ ㄩㄥˋ ㄓㄥˋ