Several transliteration systems exist for converting Mongolian script to Latin characters. The most notable ones include:

1. ISO 9: This is an internationally recognized standard for the transliteration of Cyrillic script, including Mongolian. It provides a systematic method to represent Mongolian characters in Latin script.

2. Mongolian Latin Alphabet: Developed in the early 20th century, this alphabet has undergone various revisions. The most recent version was approved in 2018, aiming to standardize the representation of Mongolian sounds using Latin characters.

3. Buryat Latin Alphabet: Used primarily for the Buryat language, this system is also applicable for transliterating Mongolian. It reflects the phonetic aspects of the Buryat language, which shares similarities with Mongolian.

4. Transliteration by Linguists: Some linguists or researchers might use their own systems or adaptations based on linguistic studies, which can vary from one study to another.

5. Online Transliteration Tools: There are also various online tools available that convert Mongolian script to Latin characters, often using one of the standardized systems mentioned above.

For further reading and resources, you can refer to the following links:

• ISO 9 Transliteration System
• Mongolian Latin Alphabet

These systems help facilitate the understanding and usage of the Mongolian language in a digital context, particularly for those unfamiliar with the traditional script.