viewimage.php?id=20bcc42e&no=24b0d769e1d32ca73dec8efa11d02831b210072811d995369f4ff39c9dd04d9df38e950baeecd192e2ee924f424fc38ffb6966c090f90e50ac36456e79eed200b882fd0fedbe06a7b0de47e55ba35794cd5e1d2ef02d734f8bc8416fe1325980ceee9f97


lower central series를 limit ordinal에 대해서도 정의하는 모양