THE MOON IS A HARSH MISTRESS by Robert A. Heinlein

TUNNEL IN THE SKY by ROBERT A. HEINLEIN

The Green Hills of Earth

Starship Troopers

Citizen of the Galaxy by Robert A. Heinlein

The Door Into Summer

I WILL FEAR NO EVIL by Robert A. Heinlein

Orphans of the Sky by Robert Heinlein

REVOLT IN 2100 By ROBERT A. HEINLEIN

ROCKET SHIP GALILEO By Robert A. Heinlein