What are the distinct cross reference source system codes which are related to the master customer details 'Gottlieb, Becker and Wyman'?
select distinct t2.source_system_code from customer_master_index as t1 join cmi_cross_references as t2 on t1.master_customer_id = t2.master_customer_id where t1.cmi_details = 'Gottlieb, becker and Wyman'