Hoya new - Kloppenburg, Dale (Robert Dale Kloppenburg, 2017)

Hoya new - Kloppenburg, Dale (Robert Dale Kloppenburg, 2018)

Hoya new - Kloppenburg, Dale (Robert Dale Kloppenburg, 2019)

Hoya pollinaria : a photographic study - Kloppenburg, Dale (D. Kloppenburg, 1996)