“…First, each unknown function in model , including and h j s ( ω ), for j = 1,…, r , u = 1,…, d , s = 1,…, q , is unidentifiable up to a constant. Following the works of Panagiotelis and Smith and Song et al, we impose the following constraint on these functions: where is the support of z , and p ( ω ) is the density function of ω .…”