Effects of pre- or post-harvest application of calcium compound extracted from oyster shell on the changes in cell wall calcium content, enzyme activity, and cell structure during storage of apple fruits Moon ByungWoo; Choi JongSeung; Kim KiHong Journal of the Korean Society for Horticultural Science 40(3): 345-348 1999 https://eurekamag.com/research/003/120/003120360.php