Note: These books are consultable on microfilm.
These letters concern not only correspondence about the Central Station, but also about other projects. Therefore, they are housed in the Cuypers Archives (code CUBA). For an index to the copybooks, see Appendix 5 in this inventory. For an index to the letters issued see: CUBA g 2009.
	
Book number Period Application number
 1 (I) 17-06-1880 to 28-11-1881 CUBA, kb 1
 2 (II) 28-11-1881 to 16-07-1883 CUBA, kb 2
 3 (III) 16-07-1883 to 30-10-1884 CUBA, cb 3
 4 (IV) 30-10-1884 to 16-03-1886 CUBA, kb 4
 5 (V) 16-03-1886 to 05-04-1887 CUBA, kb 5
 6 (VI) 09-04-1887 to 14-12-1888 CUBA, cb 6
 7 (VII) 15-12-1888 to 22-04-1891 CUBA, cb 7
 8 (VIII) 23-04-1891 to 25-08-1893 CUBA, cb 8
 9 (IX) 25-08-1893 to 22-06-1896 CUBA, cb 9
10 (X) 23-06-1896 to 22-02-1899 CUBA, cb 10
11 (XI) 30-01-1899 to 25-07-1901 CUBA, cb 11
12 (XII) 26-07-1901 to 19-07-1904 CUBA, kb 12
13 (XIII) 27-07-1904 to 21-06-1907 CUBA, kb 13
14 (XIV) 22-06-1907 to 04-03-1911 CUBA, kb 14
15 (XV) 11-03-1911 to 12-03-1915 CUBA, kb 15
16 (XVI) 15-03-1915 to 10-10-1920 CUBA, kb 16