[Republican soldiers aiming machine guns through peepholes, University City, Madrid]

[Republican soldiers aiming machine guns through peepholes, University City, Madrid]

[Men of the International Brigades in a laboratory of the Medical School building of the University City, Madrid]

[Republican soldiers behind barricade made of sandbags and luggage, University City, Madrid]

[How to make a double exposure]

[How to make a double exposure]

[How to make a double exposure]

[How to make a double exposure]