एस.आर. रंगनाथन के अनुसार, वह संदर्भ सेवा जो अवशिष्ट सिद्धांतों और सामान्यताओं से संबंधित है, जो आसानी से विशिष्ट भागों के अंतर्गत नहीं आती है, कहलाती है:

The 'Drain of Wealth' theory was propounded by which Indian nationalist leader?

Which event is considered the turning point in Mahatma Gandhi's leadership in the Indian independence movement?

Which African leader is known for his non-violent opposition to colonial rule?