On information on blue sulphide dyes

[11] 1911, FARBERZTG, P166

[12] 1897, MON SC, P655

[13] 1915, FARBERZTG, P337

[14] 1914, FARBERZEITUNG, P343

[15] 1911, FARBERZTG, P44

[16] 1918, NEW REDUCTION METHOD

[17] 1903, MON SC, P427

[18] 1916, FARBERZTG, P131

[19] 1911, FARBERZTG, P100

[20] 1912, FARBERZTG, P363

[11] 1911, FARBERZTG, P166

[12] 1897, MON SC, P655

[13] 1915, FARBERZTG, P337

[14] 1914, FARBERZEITUNG, P343

[15] 1911, FARBERZTG, P44

[16] 1918, NEW REDUCTION METHOD

[17] 1903, MON SC, P427

[18] 1916, FARBERZTG, P131

[19] 1911, FARBERZTG, P100

[20] 1912, FARBERZTG, P363