[905] Krabbe 1891, p. 131.

[906] Reinke 1894, p. 18.

[907] Bonnier, see p. 29.

[908] Darbishire, see p. 148.

[909] Tobler, see p. 148.

[910] Stahl 1877, p. 34.

[911] Paulson 1918.

[912] Paulson and Thompson 1913.

[913] Fink 1917.

[914] Baur 1901.