Gaya APA
Engels, K, M, A, F. (2005).
e-book The-Coming-Technological-Singularity .
Amerika Serikat.:
project gutenberg.
Gaya MLA
Engels, Karl, Marx, And, Friedrich.
"e-book The-Coming-Technological-Singularity".
Amerika Serikat.:
project gutenberg,
2005.
Text.