Articles:

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You are provided with multiple scientific articles above. Based on the information in these articles, answer the question provided below.

If the answer consists of multiple components (e.g., author names, article titles, reference counts), separate them with commas.
For example, if the answer includes two author names, your response should be in the format of 'the-first-author-name, the-second-author-name'.
When counting the number of words in article titles, use spaces to determine word boundaries. Words are spaced apart individually.

Respond with only the final answer, with no additional explanation or formatting. If you cannot get the answer from the articles, just return 'NULL'.

Question:

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