感謝Jorja網友和其他網友的解答~~
我原來對這句的理解是There is an unresolved controversy as to who is the real author of the Elizabethan plays which are commonly credited to William Shakespeare.(原題中 which are 被省略了)

是否是因為後面的the real author of the Elizabethan plays which are commonly credited to William Shakespeare.是一句形容詞子句 若改成間接問句的寫法 會造成文法上的錯亂 所以才將be動詞is往前寫成直接問句的寫法?

但我又有一疑問 若我把整句寫成
There is an unresolved controversy as to who the real author of the Elizabethan plays (which are省略) commonly credited to William Shakespeare is.
這樣是否可行呢?
感謝指教~