Perhaps you should try some spelling variations:
tren thuoc » trien thuoc, tren thuc, trung thuoc
thuoc sach » hoc sach, nuoc sach, thuat sach
khoa thong » hoa thong, thoai thong, khoi khong
xay khoan » may khoan, cac khoan, may khoa
khoan pho » khoan nhoi, khoan phai, khoan hoi
pho thong » he thong
sach tren » sach tien, sach tranh
sach khoa » bach khoa, sach nha, anh khoa
khoa khoa » hoa khoa, khuan khoa, khoa hoc
ki thuat » ky thuat
su sach » so sach, vu sach
sach ki » sach kinh, sach bai, sach kem
tu sach » thu sach, te sach, tu cach

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( su sach ki thuat xay khoan pho thong ) or ( tu sach tren thuoc sach khoa khoa thong ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( su sach ki thuat xay khoan pho thong ) OR ( tu sach tren thuoc sach khoa khoa thong )).
• Adding a wildcard symbol may retrieve word variants: (( su sach ki thuat xay khoan pho thong ) or ( tu sach tren thuoc sach khoa khoa thong ))*.