&\int_{0}^{T}\int_{0}^{\varepsilon }\int_{0}^{\varepsilon }\int_{0}^{T}G_{\varepsilon }(s,t,s^{\prime },t^{\prime })\,\mathrm{d}s\,\mathrm{d}t\,\mathrm{d}s^{\prime }\,\mathrm{d}t^{\prime}, \\ H_{\varepsilon }^{0} &=&-\int_{0}^{T}\int_{