Several "group theories" have also been proposed.
1	Several	several	DET	DI	PronType=Ind	4	det	_	_
2	"	"	PUNCT	FB	_	4	punct	_	SpaceAfter=No
3	group	group	NOUN	S	Number=Sing	4	nmod	_	_
4	theories	theory	NOUN	S	Number=Plur	9	nsubj:pass	_	SpaceAfter=No
5	"	"	PUNCT	FB	_	4	punct	_	_
6	have	have	AUX	VA	Mood=Ind|Number=Plur|Tense=Pres|VerbForm=Fin	9	aux	_	_
7	also	also	ADV	B	_	9	advmod	_	_
8	been	be	AUX	VA	Tense=Past|VerbForm=Part	9	aux:pass	_	_
9	proposed	propose	VERB	V	Tense=Past|VerbForm=Part	0	root	_	SpaceAfter=No
10	.	.	PUNCT	FS	_	9	punct	_	_
