I have a crossing table that translate some data through 2 different DB

In the first DB i have a table

tableA
----------------
id_userA
city_code
(other not important field)

In the second DB the city code is structured in a different mode

tableB
----------------
id_userB
city_cod1
city_cod2
city_cod3
(other not important field)


The anagraphic of the cities is in the first DB so I created a translation table that match the 3 codes of the second DB to the code of the first DB

translate_table
----------------
city_code (PK)
city_cod1
city_cod2
city_cod3

city_cod1, city_cod2, city_cod3 as an index (unique)

This table makes only a translation of the coding between the two different DB

I tryed different configuration like

in tableB .hbm.xml

<property name="cityCod1" type="java.lang.String" column="city_cod1" length="3" />
<property name="cityCod2" type="java.lang.String" column="city_cod2" length="3" />
<property name="cityCod3" type="java.lang.String" column="city_cod3" length="3" />

<properties name="codB">
<property name="cityCod1" column="city_cod1" insert="false" update="false"/>
<property name="cityCod2" column="city_cod2" insert="false" update="false"/>
<property name="cityCod3" column="city_cod3" insert="false" update="false"/>
</properties>

<join table="translate_table">
<key property-ref="codB" not-null="true" >
<column name="city_cod1" />
<column name="city_cod2" />
<column name="city_cod3" />
</key>
<many-to-one name="tableA" class="tableA" not-null="true" column="city_code" />
</join>

but i have this error

Configuration problem: Foreign key (FKABD26E567A5262DA:translate_table [city_cod1,city_cod2,city_cod3])) must have same number of columns as the referenced primary key (tableB [id_userB])

How i can modelling this Database structure

Thanx Ivan