The pronoun 兹
We only use the demonstrative pronoun 兹 
in written speech. It refers to an object that is relatively close to the speaker.
For example:
兹日
兹赠
兹臣庶
in written speech. It refers to an object that is relatively close to the speaker.
For example:
兹日
兹赠
兹臣庶 Pay attention
Demonstrative pronouns (指示代词) are used to indicate an object that the speaker is referring to.
Examples
兹协议从今天开始有效
This agreement is effective as of today
zī xiéyì cóng jīntiān kāishǐ yǒuxiào
兹理易明
This is easy to understand
zī lǐ yì míng