A Retrospective Exhibition of Artists' Billboards of the Last 30 Years A Retrospective Exhibition of Artists'Billboards of the Last 30 Years Billboard Art on the Road：A Retrospective Exhibition of Artists' Billboards of the Last 30 Years Retrospective of Hong Kong films over the last 30 years a Retrospective Exhibition on the Art of Huang Bore Retrospective exhibition of Ding Yanyong's art