Question

Name all important source of directive principles?

Answer 1

Indian constituition has taken many points from many other constitutions like
Italy
French
Dutch and
United States of America

Answer 2

The Directive Principles of State Policy of Indian Constitution are inspired from Irish Constitution which took the details from Spanish Constitution itself.
Also, the Government of India Act, 1935 had some Instruments of Instructions which also became the immediate source of DPSP.
Another sources that can be identified is Sapru Report, 1945 which gave us both Fundamental Rights (justiciable) and DPSP (non justiciable).