Perhaps you should try some spelling variations:
doanh khoa » toan khoa
thai vung » thai cong, thai van
vung tuan » vuong tuan, hung tuan, vong tuan
thu sach » tu sach, thuat sach, thuoc sach
sach hoc » cach hoc, sach hoi, mach hoc
khoa hoc » hoa hoc
tuan van » luan van, tran van, tan van
long so » long soc, cong so, long o
dong so » dong son, dong co, cong so
xa thai » ca thai, a thai, da thai
hoc xa » hoc ma

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: thu sach hoc tap, nghien cuu ((long so) or (dong so)) doanh khoa hoc xa thai vung tuan van~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach hoc tap, nghien cuu ((long so) OR (dong so)) doanh khoa hoc xa thai vung tuan van.
• Adding a wildcard symbol may retrieve word variants: thu sach hoc tap, nghien cuu ((long so) or (dong so)) doanh khoa hoc xa thai vung tuan van*.