“…Subsequently, these topics attract attention of many mathematicians from different disciplines. For diverse studies and applications on these topics, see Chang [4], Chang, Pearson and Zhang [5], Chang, Pearson and Zhang [6], Hu, Huang and Qi [8], Hu and Qi [7], Ni, Qi, Wang and Wang [15], Ng, Qi and Zhou [16], Song and Qi [23,24], Yang and Yang [26,27], Zhang [28], Zhang and Qi [29], Zhang, Qi and Xu [30] and references cited therein.…”