Table 1: The order of singularity of the solution and the functions 𝑊 𝑛 𝑘 , 𝑖 .

𝑙 𝑙 1 𝑙 2 𝑙 3 𝑝 4 3 2

0 𝑊 4 2 , 𝑖 𝑊 2 1 , 𝑖
1 𝑊 3 1 , 𝑖
2 𝑊 4 1 , 𝑖 𝑊 2 0 , 𝑖
3 𝑊 3 0 , 𝑖
4 𝑊 4 0 , 𝑖
𝑝 2 𝑞 𝑊 𝑝 𝑞 , 𝑖
𝑙 3 𝑊 𝑙 1 1 , 𝑖 𝑊 𝑙 3 0 , 𝑖
𝑙 2 𝑊 𝑙 1 , 𝑖 𝑊 𝑙 2 0 , 𝑖
𝑙 1 𝑊 𝑙 1 0 , 𝑖
𝑙 𝑊 𝑙 0 , 𝑖