Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_60420 ( "Tie no" text, "Home team" text, "Score" text, "Away team" text, "Date" text )

### Question ###
What was the tie number for the game with an away team of Hartlepool United?

### Accurate SQL ###

SELECT "Tie no" FROM table_60420 WHERE "Away team" = 'hartlepool united'