**Acknowledgements**

The authors extend their gratitude to Mrs. Nilakshi Jayawardena, Ms. Mindani Watawana and Mrs. Chaminie B. Gunawardhana, who were former Research Assistants/Postgraduate Students at the National Institute of Fundamental Studies, Kandy, Sri Lanka. This work was partially supported by grants-in-aid from the School of Human Sciences at Kobe College, Japan.
