2 sentences

1. 这是一封推荐信。

   zhè shì yī fēng tuī​jiàn​xìn.

   This is a letter of recommendation.

   Source: OpenSubtitles

2. 申请这所大学需要两封推荐信。

   shēn​qǐng zhè suǒ dà​xué xū​yào liǎng fēng tuī​jiàn​xìn.

   Two letters of recommendation are required to apply to this university.

   Source: Dong Chinese Dictionary