Declension table of ?śirasya

Neuter	Singular	Dual	Plural
Nominative	śirasyam	śirasye	śirasyāni
Vocative	śirasya	śirasye	śirasyāni
Accusative	śirasyam	śirasye	śirasyāni
Instrumental	śirasyena	śirasyābhyām	śirasyaiḥ
Dative	śirasyāya	śirasyābhyām	śirasyebhyaḥ
Ablative	śirasyāt	śirasyābhyām	śirasyebhyaḥ
Genitive	śirasyasya	śirasyayoḥ	śirasyānām
Locative	śirasye	śirasyayoḥ	śirasyeṣu

Compound śirasya -

Adverb -śirasyam -śirasyāt