求翻译：在特殊函数常微分方程理论中，把一些变系数常微分方程可以通过适当的变换而化为贝塞尔方程的方程，我们把此类方程定义为贝塞尔类方程。在文献【1】中分析并给出了寻找此类变化的可循路径，但是，我们可以看出寻找此类变换的方法有一定的难度，而且较为繁杂。是什么意思？

Some variable coefficients often in special function theory of ordinary differential equations, differential equations can be through the appropriate transformation into the equation of the Bessel equation, we have such equations is defined as the Bessel class of equations. Analysis in the literatur

In the special function theory, differential equations often have some variable coefficients can be used with differential equations and the appropriate transformation for Bessel equation, we have the equations such equations are defined as the class equation. In the literature [ 1] The analysis and