A carrying case apparatus having a case body and one or more elastic straps coupled to the case body forming a sleeve for receiving an audio headset. Soft links are created and associated with content nodes by having a reference pointer to a node that is resolved by the content repository. The rake retractor broadly includes a shaft coupled to a plurality of free ends. The voucher server determines if the received identifier matches an identifier of any of the plurality of encrypted digital vouchers. The frequency-dependent bias method has been found effective with GNSS observations from a combination of substantially dissimilar hardware, e.