Found the following hamletworks.org entries referring to line 343

View Commentary Note for 343
343 But breake my hart, for I must hold my tongue.1.2.159

View Immaterial Textual Note for 343
343 But breake my hart, for I must hold my tongue.1.2.159

View Material Textual Note for 343
343 But breake my hart, for I must hold my tongue.1.2.159

View Commentary Note for 374
374 Ham. In my mindes eye Horatio.1.2.185