1. Allen, R. C. 1932. Factors influencing the color of hydrangea. Proc. Amer. Soc. Hort. Sci. 28: 410–412.
2. Allen, R. C. 1943. Influence of aluminum on the flower color of Hydrangea macrophylla D.C. Contrib. Boyce Thompson Inst. 13: 221–242.
3. Asen, S. and H. W. Siegelman. 1957. Effect of aluminum on absorption spectra of the anthocyanin and flavonols from sepals of Hydrangea macrophylla var. Merveille. Proc. Amer. Soc. Hort. Sci. 70: 478–481.
4. Asen, S., H. W. Siegelman and N. W. Stuart. 1956. Anthocyanin and other phenolic compounds in red and blue sepals of Hydrangea macrophylla var. Merveille. Proc. Amer. Soc. Hort. Sci. 69: 561–569.
5. Chenery, E. M. 1937. The problem of the blue hydrangea. J. R. Hort. Soc. 62: 320–604.