Characterization of envelope sequence of HIV virus in children infected with HIV in Vietnam oleh Linh Vu Phuong Dang, Hung Viet Pham, Thanh Thi Dinh, Thu Hoai Nguyen, Quyen Thi Huyen Vu, Nhung Thi Phuong Vu, Phuong Thi Bich Le, Lam Van Nguyen, Hai Thanh Le, Phuong Thi Vu, Linus Olson