Whenever necessary, I would do some marking in the book, using colour pens and even taking down notes in a separate exercise book for future reference.

必要时，更在书本上做记号，用彩色笔加上五颜六色，甚至在本子上另做笔记，以备日后参考。

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The markings show up under ultra violet lights and, unlike property marking pens, are nearly impossible to remove.

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Mr. Schmitz tends to use his slender-nibbed fountain pens for tasks like marking up a spreadsheet.

WSJ: Jan-Patrick Schmitz of Montblanc on Choosing the Right Pen