<|begin_of_text|><|start_header_id|>system<|end_header_id|>

You are an expert at identifying data availability statements in scientific text. A data availability statement describes where research data can be found or how it can be accessed.<|eot_id|><|start_header_id|>user<|end_header_id|>

Determine if the following text contains a data availability statement. Answer with 'yes' or 'no'.

Text: the authors confirm that, for approved reasons, some access restrictions apply to the data underlying the findings. data used in this paper are from chinese national hiv sentinel surveillance program, and guangzhou center for disease control and prevention owns the data. data are available upon request. such a request should be sent to dr. huifang xu (gzxuhuifang@hotmail.com), the director of hiv sentinel surveillance program at guangzhou center for disease control and prevention.<|eot_id|><|start_header_id|>assistant<|end_header_id|>

yes<|eot_id|>