用于申请签证的学习计划(Study Plan)，情况说明函（Explanatory Letter）和申诉信（Letter of Appeal）等文件并非每个国家的使馆都需要，同样，这些文件对不同国家的签证官所能产生的效果也不尽相同。
双语例句
1
Upon those, had followed gabelles letter: the appealof an innocent prisoner, in danger of death, to his justice, honour, and good name.
何况还有加伯尔的信：一个无辜的囚徒，有了生命危险，要求他给予正义荣誉和切实的名分。
2
Filing period: An appeal must be filed within the time period provided in the letterof notification or within 30 days from receipt of the notification, whichever occurs later.