Jakarta, NU Online
In the old (salafi) pesantren (Islamic boarding school) learning system, there is a method of study by using yellow book (kitab kuning). This book is an Arabic-language book without a vowel (harakah) or commonly referred locally to as the Arab Gundul.<>

According to an observer of Islamic education of UIN Syarif Hidayatullah Jakarta, Prof. Abuddin Nata, the yellow book contains about the interpretation of hadith, aqidah, Sufism, or morality, the science of kalam, fiqh, history, and culture of Islam. 
It also contained the Arabic language lessons as well as its derivatives such as nahwu, sharaf, balaghah, and others. There are also subjects of humanities, stories, fairy tales and saga.

The book is known as the yellow book because the paper used was yellow paper. In the past, there has been no kind of white paper like today.

Yellow paper becomes an important material for writing books about students study. Printing of the book was just using simple tools; the layout is monotonous and rigid.

There was also book bound with neat, but only given a cover with a thicker paper and bound potluck. In the past, the yellow book printing was considered good when compared with the original handwriting manuscript.

Other information obtained from salaf.web.id page, mentioned that the yellow color of the paper is considered more convenient and easy to read in dim circumstances.

In the old days, when light was limited, the students especially those in the villages used to read books with makeshift lighting in the evening.

Although, electricity was not a problem for now, books with yellow paper still survive, in order to preserve the tradition. However, there are several books available with the same contents as the yellow book, but it printed using HVS white paper.

In fact, yellow book content has been digitalized with a computer through pdf format. However, the price of the yellow books was much cheaper.

The contents of the yellow book are the result of scientific works of the scholars of the past. One of the books is fiqh, which is the result of codification and legal istimbath derived from the Qur'an and Sunnah.

The students studied the book with the guidance of a Kiyai (cleric) in pesantren. Then, the teaching of the book taught to the public. Typically, each Kiyai in pesantren had each expertise on the specific yellow book.

For example, Pondok Pesantren Tebu Ireng known widely expert in the book of Hadith Sahih Bukhari. Although the boarding school has specialist expertise, other sciences and subjects are also delivered to student.

Editing by Sudarto Murtaufiq