There are two theories about this: one says that although the set was originally complete, some chapters got lost later and were supplemented by manuscripts written in other hands; another says that the chapters written in other hands were paired with the set when it was made in the first place.
これについて、元々揃っていたのだがあるとき欠けてしまい、別人の手になる巻で補ったとする考え方と最初に作られた時から別人の手になる写本とセットになっていたとする考え方とがある。