Co-authorship: a book or paper written jointly by two or more authors.
彼らはその専門書を共著で出版した。
They published that specialist book as co-authors.
学会誌に共著の論文が掲載された。
A co-authored paper was published in the journal of the academic society.
この論文は〇〇教授と私の共著だ。
This paper is co-authored by Professor XX and me.