Problem with the column

Hi,
I don't know why I get this

OLE DB provider "OraOLEDB.Oracle" for linked server "ORA_SYS" returned message "ORA-00904: "OB_OLD": invalid identifier".

with this script

CREATE VIEW [dbo].[vw_ite_tab]
AS
select ...
OB_OLD,
...
from ite_tab
where substr(ite_FROM,1,2) in(''BK'',''TO'',''NP'')
AND trunc(LAST_UPDATE_DATE)=trunc(sysdate)') oq 

while the relevant column has been declared within Oracle, like

 OB_OLD                                                              CHAR(1 CHAR)

Many Thanks & Best Regards, Hua Min