Recently, YANG Xiaolin and his collaborators from Yunnan Observatories of the Chinese Academy of Sciences developed a new fast code, Lemon (Linear Integral Equations' Monte Carlo Solver Based on Neumann Solution), aiming to solve the radiation transfer processes (RTPs) precisely. The scheme of the code is based on linear integral equation and its Neumann series solution. The study was published in The Astrophysical Journal Supplement Series.