A fluorescent marking composition containing particles of an organic material which has a glass transition temperature of at least 30.degree. C. and an average particle size of at least 30 nm, and emitting fluorescence in a visible light range, or absorbing infrared light having a wavelength of at least...http://www.google.com.au/patents/US5880176?utm_source=gb-gplus-sharePatent US5880176 - Fluorescent marking composition and fluorescent mark formed by said composition
