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- Letter Peter Jacob van Mulken to his son in Holtum, 1862
- Letter Peter Jacob van Mulken to his brother-in-law, 1862
- Letter Wilhelmus Paulussen to his family, May 1863
- Letter Henri Strauss as a reaction to the letter of Wilh. Paulussen, June 1863
- Letters of Peter Engels and Simon Timmermans respond to the letter of Henri Strauss, June 1863
- Letter Peter Joseph Schaps to his uncle in Birgden, 1865