You may also wish to search for items by Hughes, M. and Hughes.
Only one matching reference was found.
Kite, G.C.; Hughes, M.J., Analysis of hydroxypipecolic acids by gas chromatography-mass spectrometry, Phytochem. Anal., 1997, 8, 6, 294-300, https://doi.org/10.1002/(SICI)1099-1565(199711/12)8:6<294::AID-PCA372>3.0.CO;2-R . [all data]