Found the following hamletworks.org entries referring to line 280
View Immaterial Textual Note for 271
271
But you must knowe your father lost a father,
1.2.89
View Commentary Note for 280
280
For what we knowe must be, and is as common
1.2.98
View Immaterial Textual Note for 280
280
For what we knowe must be, and is as common
1.2.98
View Material Textual Note for 280
280
For what we knowe must be, and is as common
1.2.98