Upadhyaya, K.N., author
Vikas Publishing House, 1994
Buku Teks
Moeller, Therald, author
John Wiley & Sons, 1952
Buku Teks
KAT International Marketing Service, 1972
Buku Referensi
Stevens, Erland, author
Pearson, 2014
Buku Teks
Barnett, E. de Barry, author
Longman, 1957
Buku Teks