An Trung Nguyen, Thi Cam Ha Nguyen, Tien Thinh Lai, Hoang Giang Nguyen, Ha Vu and Thanh Long Nguyen 2021. Developing a database for Cs-137 radioactivity concentration and assessing residual levels in surface soils of Quang Ninh, Hai Phong, and Lang Son provinces. Vietnam Journal of Science, Technology and Engineering. 63, 3 (Sep. 2021), 92-96. DOI:https://doi.org/10.31276/VJSTE.63(3).92-96.