law: The Indian Succession Act, 1925
  Chapter III.- Of the Execution of unprivileged Wills
  63. Execution of unprivileged wills.-
  Every testator, not being a soldier employed in an expedition or engaged in actual warfare, 1[or an airman so employed or engaged,] or a mariner at sea, shall execute his will according to the following rules:-
  (a) The testator shall sign or shall affix his mark to the will, or it shall be signed by some other person in his presence and by his direction.
  (b) The signature or mark of the testator, or the signature of the person signing for him, shall be so placed that it shall appear that it was intended thereby to give effect to the writing as a will.
  (c) The will shall be attested by two or more witnesses, each of whom has seen the testator sign or affix his mark to the will or has seen some other person sign the will, in the presence an d by the direction of the testator, or has received from the testator a personal acknowledgment of his signature or mark, or of the signature of such other person; and each of the witnesses shall sign the will in the presence of the testator, but it shall not be necessary that more than one witness be present at the same time, and no particular form of attestation shall be necessary.
  64. Incorporation of papers by reference.-
  If a testator, in a will or codicil duly attested, refers to any other document then actually written as expressing any part of his intentions, such document shall be deemed to form a part of the will or codicil in which it is referred to.