Glossary of Plant Systematics (1st ed.) by Simpson (2006)
- A component of the perianth in which the parts intergrade or in which the perianth is undifferentiated into distinctive sepals and petals. (flower part, perianth part)
Glossary of "Life (9th ed.)" by Sadava et al. (2011)
- A sterile, modified nonphotosynthetic leaf of an angiosperm flower that cannot be distinguished as a petal or a sepal.
Glossary of "Flora of Okinawa and the Southern Ryukyu Islands" by Walker (1976)
- Used in the plural for sepals and petals together when these are of similar form and not readily differentiated. 花被片，花蓋片
- Simpson, M. G. 2006. Plant Systematics. -xi + 590 pp. Elsevier Academic Press, Oxford.
- Sadava, D., Hillis, D. M., Heller, H. C. & Berenbaum, M. R. 2011. Life: The Science of Biology, 9th ed. -xliv + 1266 pp. Sinauer Associates, Inc., Sunderland.
- Walker, E. H. 1976. Flora of Okinawa and the Southern Ryukyu Islands. ix + 1159 pp. Smithsonian Institution Press, Washington, D. C.