<|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: this study utilized a total of 20 topographic maps which were acquired in 1968 and derived from aerial photographs taken by the state bureau of surveying and mapping. the us geological survey (usgs; http://glovis.usgs.gov) and the global land cover facility provided the landsat images. the meteorological data were downloaded from the china meteorological data sharing service system (http://cdc.cma.gov.cn). all maps were obtained from the national geomatics center of china under a confidentiality agreement. researchers interested in accessing the maps should apply to the national geomatics center of china, 28 lianhua road, haidian district, beijing. the lake area data for 1991, 2001, and 2013 are within the supporting information files.<|eot_id|><|start_header_id|>assistant<|end_header_id|>

yes<|eot_id|>