You will be given a definition of a task first, then some input of the task.
In this task, you will be presented with a context from an academic paper and a question separated with a
. You have to answer the question based on the context.

Maximum matching (MM) is one of the most popular fundamental and structural segmentation algorithms for word segmentation BIBREF19 . However, it does not solve the problem of ambiguous words and unknown words that do not exist in the dictionary.
Question: What are the limitations of existing Vietnamese word segmentation systems?
Output:
ambiguous words unknown words