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DOI: 10.1080/02678299208029010

Kitzerow, H.-S., Xu, F., &; Crooker, P. P. (1992). Microscopic observations of axial and radial nematic droplets for a dual-frequency addressable liquid crystal. Liquid Crystals, 12(6), 1019–1024.https://doi.org/10.1080/02678299208032817 
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Heppke, G., Kitzerow, H.-S., Lötzsch, D., &; Papenfuß, Ch. (1990). Blue phase mixtures exhibiting low fractions of a chiral compound experimental observation of some unusual properties. Liquid Crystals, 8(3), 407–418.https://doi.org/10.1080/02678299008047356 
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Heppke, G., Jéròme, B., Kitzerow, H.-S., &; Pieranski, P. (1989). Observation of a hexagonal blue phase in systems with negative dielectric anisotropy. Liquid Crystals, 5(3), 813–828.https://doi.org/10.1080/02678298908026387 
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