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 CMI_Cross_References ( cmi_cross_ref_id VARCHAR, source_system_code VARCHAR )
TABLE: CREATE TABLE Council_Tax ( cmi_cross_ref_id VARCHAR )

### Question ###
What is the cmi cross reference id that is related to at least one council tax entry? List the cross reference id and source system code.

### Accurate SQL ###

SELECT T1.cmi_cross_ref_id, T1.source_system_code FROM CMI_Cross_References AS T1 JOIN Council_Tax AS T2 ON T1.cmi_cross_ref_id = T2.cmi_cross_ref_id GROUP BY T1.cmi_cross_ref_id HAVING COUNT(*) >= 1