参考文献

Uppala, Venkata Bhaskara Rao; Vaddadi, Pattabhi Ramayya; Sunkara, Vishnu Vardhan; Cheemalapati, Venkata Annapurna Sasikala; Padaga, Kanaka Seshu Kumar Patent: US2007/49748 A1, 2007 ; Location in patent: Page/Page column 9 ;