1. Drilling versus broadcasting of grain;Heege;American Society of Agricultural Engineers. Paper No. 69–165,1969
2. Kornverteilung uber die Flache und Ertrag bei Getreide;Mülle;Zeitschrift für Acker-und Pflanzenbau,1981
3. The merits of precision drilling and broadcasting for the establishment of cereal crops in Britain;Graham;ADAS Quarterly Review,1980
4. Precision drilling of cereals;Roebuck;Experimental Husbandry,1978
5. The effect of plant density upon the growth and yield of spring barley;Kirby;Journal of Agricultural Science,1967