(1)Dimensionality Reduction: A Comparative Review的P15頁The presence of free parameters has both advantagesand disadvantages. The main advantage of the presence of free parameters is that they provide more flexibility to the technique, whereas their main disadvantage is that they need to be tuned to optimize the performance of the dimensionality reduction technique.
(2)Zhongqiu Zhao's Ph.D. thesis P87:雖然此參數可能會給半監督學習帶來可靈活機動的好處，但是同時它也增加了程序調試的難度。
(3)Fei Wang's Ph.D. thesis P13:圖上半監督學習算法大都需要用高斯函數(式(1-6))計算數據之間的相似度，并且該函數中的自由參數\sigma是需要由用戶指定的，這給這類算法在實際中的應用帶來了很大的麻煩。