Pāṇini sūtras

There is optionally the substitution of ā in the room of the diphthong of the roots ci and sphura when in the Causative.

German Desgleichen in ci und sphur im Causativum. (54)

1. ci+sphuroḥचि+स्फुरोः

   Part	Lexeme	Sandhi form	Meaning	Stem + termination
   cच्	ciचि	ciचि	ciचि	cच् + plus iइ
   sस्	sphurस्फुर्	sphuroḥस्फुरोः	sphurस्फुर्	sphurस्फुर् + plus oḥओः

2. ṇauणौ

   Part	Lexeme	Sandhi form	Meaning	Stem + termination
   ṇण्	ṇiणि	ṇauणौ	causative	ṇण् + plus auऔ

Anuvṛtti

1. upadeśeउपदेशे 6·1·45

   Part	Lexeme	Sandhi form	Meaning	Stem + termination
   uउ	upadeśaउपदेश	upadeśeउपदेशे	linguistics	upadeśउपदेश् + plus eए

2. vibhāṣāविभाषा 6·1·51

   Part	Lexeme	Sandhi form	Meaning	Stem + termination
   vव्	vibhāṣविभाष्	vibhāṣāविभाषा	option	vibhāṣविभाष् + plus āआ