This is a sample infobox showing how to include the <references /> tag within the template itself. This is done with {{reflist}} and the group parameter.
{{Infobox
|title = Sample infobox
|label1 = Label1
|data1 = Data1<ref group=note>Reference 1</ref>
|label2 = Label2
|data2 = Data2<ref group=note>Reference 2</ref>
|label3 = Label3
|data3 = Data3
|label4 = Label4
|data4 = Data4
|belowstyle = text-align:left;
|below = {{reflist|group=note}}
}}