Relation Table With Same Field From 2 Table

I have problem for create relation between table. I have one table refer to 2 table with same field. Here's the code.

create table TopHeadConfTbl (
PartNumber varchar(14) primary key not null,
TpHdTypeID varchar(4) not null)

create table BotHeadConfTbl (
PartNumber varchar(14) primary key not null,
BotHdTypeID varchar(4) not null)

create table QuoDetTbl(
MainAsID varchar(14)not null,
PartNumber varchar(14) not null references (TopHeadConfTbl,BotHeadConfTbl) ,
ItemNumber varchar(14) notnull)