Please tell me the International Standard Book Number of this book.

The International Workers' Association is historically an important organization.

He is exactly in the state of 'A frog in a well does not know the vast ocean.'

He spoke of his big dreams, saying, 'How can a sparrow understand the ambitions of a swan?'

He can speak Min Nan.

Learning Breton language is difficult.

Learning the Erzya language is difficult.

Learning Faroese is difficult.

He is learning the Cornish language.

I am learning Modern Greek.