which museum exhibits the portrait of a young man by sandro botticelli ?
select distinct var_uri where brack_open dbr_Portrait_of_a_Young_Man_ attr_open Botticelli,_London attr_close dbo_museum var_uri sep_dot dbr_Portrait_of_a_Young_Man_ attr_open Botticelli,_London attr_close dbo_author dbr_Sandro_Botticellibrack_close