The Technique of Travel : Page 139
In descending steep slopes at night it is safest to sideslip.
Uniform distress signal.—A man or party who, be-yound question of doubt, requires aid should give three signals (=SOS) of any sort, audible or visual, at frequent intervals. A yell is perhaps the least satisfactory signal, because it will soon tire the vocal cords, and, unfortunately, is often mistakenly assumed not to be a call of distress. The call for help is acknowledged by two signals (=0K) and an immediate attempt to help.
The skier who is lost should follow the maxim, "stay warm and keep cool." He must waste no effort. He should: