How to write Xi 'an in English?

Phrases:

Xi 'an Xi 'an; Xi an; Metro Line 2; collapse

Hilton Xi An Wanda Hilton Hotel Xi 'an

Xi' an hotel an restaurant

Xi 'an population Xi 'an population expansion data example:

I am also a college student. "I feel sorry for you," said Liu Zhuoya from the northwest city of Xi.

Liu Zhuoya, a netizen from the northwest city of Xi, said, "I am also a college student, and I am sorry to hear your story."

Yue, a researcher at Xi 'an Animal Husbandry Technology Center, said that sheep and dogs are different species.

According to Yue, a researcher at An Animal Husbandry Technology Extension Center, sheep and dogs belong to different species.