Hellgren, O. (1984). Acclimation to quantum flux density, temperature and photoperiod as effects on growth, development, chlorophyll content and leaf characteristics in Pelargonium zonale hybr. Swedish University of Agricultural Sciences.
توثيق أسلوب شيكاغو (الطبعة السابعة عشر)Hellgren, Olof. Acclimation to Quantum Flux Density, Temperature and Photoperiod as Effects on Growth, Development, Chlorophyll Content and Leaf Characteristics in Pelargonium Zonale Hybr. Alnarp: Swedish University of Agricultural Sciences, 1984.
توثيق جمعية اللغة المعاصرة MLA (الطبعة الثامنة)Hellgren, Olof. Acclimation to Quantum Flux Density, Temperature and Photoperiod as Effects on Growth, Development, Chlorophyll Content and Leaf Characteristics in Pelargonium Zonale Hybr. Swedish University of Agricultural Sciences, 1984.