1. Chiba Agricultural Experiment Station (CAES) (1976) Vegetable hand book (in Japanese). Chiba, Japan
2. Ebise S (1984) Estimation of total pollutant loading by all influent rivers into Lake Kasumigaura (in Japanese). Res Rep Nat Inst Env Stud 50:41?58
3. Ibaraki Prefecture (2003) Ibaraki Prefecture environment white paper H15 (in Japanese). Ibaraki, Japan
4. Ibaraki Prefecture (1981?1999) Monitoring data of public water (in Japanese). Ibaraki, Japan
5. Ibaraki Prefecture Life Environment Department Kasumigaura Countermeasure Section (IPLEDKCS) (1999) The report to the lake water quality preservation plan in Kasumigaura basin (the 3rd term) (in Japanese). Ibaraki, Japan