By the way
... themselves(反身代词)他(她,它)们自己 by the way顺便一提 made很生气的 ...
Incidentally
... proportion n. 比例,部分 incidentally adv. 顺便一提;偶然地 cover v. 包括,涉及 ...
incidentally ; BTW
incidentally ; incidentally ad
by the way