yán / jiū / zhè / duàn / lì / shǐ / shí / wǒ / men / xū / yào / liǎo / jiě / dāng / shí / de / xí / guàn / fǎ

研究这段历史时，我们需要了解当时的习惯法。

When studying this period of history, we need to understand the customary law of the time.