Lee Ka-sing began his diptych project in 2014. Over the years, more than a thousand diptychs were created. He describes the project as spontaneously as brush strokes on the pages of a sketchbook, or, a poem written daily. These are juxtapositions of volumes of photographs from his current and previous work. In 2019, based on selections from this body of work, he begins to issue Archive Prints as part of his BIBLIOTHEKA series, in open edition and individual BIBLIOTHEKA prints. Besides, the diptychs also serve as parts of stanzas, or lines, of book-length poems in artist-book format. His first BIBLIOTHEKA artist-book HONG KONG TWO VISITS, was created in 2018.