Staszewski, Z., 1980: A method of breeding heterotic lucerne hybrids. Biuletyn Instytutu Hodowli i Aklimatyzacji Roslin (142): 6
For the production of single hybrids, male-sterile lines of the maternal variety should be pollinated by self-sterile clones, a procedure that ensures that all plants of the next generation are hybrid. The procedure for obtaining double hybrids is also set out. Among the criteria adopted for the selection of the component lines, a high value for combining ability should be regarded as important.