JOHNSEN, Kurt H. Negative heterosis not apparent in 22-year-old hybrids of Picea mariana and Picea rubens. In Can. J. Bot., 1998, roč. 76, s. 434-439Error: read handle in (rep.epca.fmtISO690).fmtXDatabaze. Dostupné na internete: <https://cdnsciencepub.com/doi/abs/10.1139/b98-002>