According to the protocol of the days, if their rank were equal, it should have been written as 'To Yuki Mandokoro from Ashikaga Sama no kami Nyudo' (Samano no kami literally means Head of the Left Stable, a rank from before the Nara period); but the Ashikaga clan were allowed to write under such a format as they were a Monyo (blood line) of the shogun family and permitted to use the family name of Minamoto clan.
通常、対等の関係であるならば、「結城政所殿　足利左馬頭入道」と記すべきところではあったが、足利氏は将軍家の門葉として源姓を称することを許されており、このような書式を用いることを許されていた。