diff --git a/src/solanaceae/zox/ngc.cpp b/src/solanaceae/zox/ngc.cpp
index 5830c1e..fa56d8a 100644
--- a/src/solanaceae/zox/ngc.cpp
+++ b/src/solanaceae/zox/ngc.cpp
@@ -38,13 +38,11 @@ std::optional<std::pair<uint8_t, uint8_t>> parse_zox_pkg_header(const uint8_t* d
 	return std::make_pair(version, pkt_id);
 }
 
-void ZoxNGCEventProvider::subscribeToEvents(void) {
-	_tep.subscribe(this, Tox_Event_Type::TOX_EVENT_GROUP_CUSTOM_PACKET);
-	_tep.subscribe(this, Tox_Event_Type::TOX_EVENT_GROUP_CUSTOM_PRIVATE_PACKET);
-}
-
-ZoxNGCEventProvider::ZoxNGCEventProvider(ToxEventProviderI& tep) : _tep(tep) {
-	subscribeToEvents();
+ZoxNGCEventProvider::ZoxNGCEventProvider(ToxEventProviderI& tep) : _tep_sr(tep.newSubRef(this)) {
+	_tep_sr
+		.subscribe(Tox_Event_Type::TOX_EVENT_GROUP_CUSTOM_PACKET)
+		.subscribe(Tox_Event_Type::TOX_EVENT_GROUP_CUSTOM_PRIVATE_PACKET)
+	;
 }
 
 bool ZoxNGCEventProvider::onZoxGroupEvent(
diff --git a/src/solanaceae/zox/ngc.hpp b/src/solanaceae/zox/ngc.hpp
index d78405a..694e88b 100644
--- a/src/solanaceae/zox/ngc.hpp
+++ b/src/solanaceae/zox/ngc.hpp
@@ -108,11 +108,9 @@ struct ZoxNGCEventI {
 using ZoxNGCEventProviderI = EventProviderI<ZoxNGCEventI>;
 
 class ZoxNGCEventProvider : public ToxEventI, public ZoxNGCEventProviderI {
-	ToxEventProviderI& _tep;
+	ToxEventProviderI::SubscriptionReference _tep_sr;
 	//ToxI& _t;
 
-	void subscribeToEvents(void); // private
-
 	public:
 		ZoxNGCEventProvider(ToxEventProviderI& tep/*, ToxI& t*/);
 
diff --git a/src/solanaceae/zox/ngc_hs.cpp b/src/solanaceae/zox/ngc_hs.cpp
index 737ce29..bf786d4 100644
--- a/src/solanaceae/zox/ngc_hs.cpp
+++ b/src/solanaceae/zox/ngc_hs.cpp
@@ -14,17 +14,15 @@
 #include <vector>
 #include <algorithm>
 
-void ZoxNGCHistorySync::subscribeToEvents(void) {
-	_zngcepi.subscribe(this, ZoxNGC_Event::ngch_request);
-	_zngcepi.subscribe(this, ZoxNGC_Event::ngch_syncmsg);
-
-	_tep.subscribe(this, Tox_Event_Type::TOX_EVENT_GROUP_PEER_JOIN);
-}
-
 ZoxNGCHistorySync::ZoxNGCHistorySync(ToxEventProviderI& tep, ZoxNGCEventProviderI& zngcepi, ToxI& t, Contact3Registry& cr, ToxContactModel2& tcm, RegistryMessageModelI& rmm)
-	: _tep(tep), _zngcepi(zngcepi), _t(t), _cr(cr), _tcm(tcm), _rmm(rmm), _rng(std::random_device{}())
+	: _tep_sr(tep.newSubRef(this)), _zngcepi_sr(zngcepi.newSubRef(this)), _t(t), _cr(cr), _tcm(tcm), _rmm(rmm), _rng(std::random_device{}())
 {
-	subscribeToEvents();
+	_tep_sr.subscribe(Tox_Event_Type::TOX_EVENT_GROUP_PEER_JOIN);
+
+	_zngcepi_sr
+		.subscribe(ZoxNGC_Event::ngch_request)
+		.subscribe(ZoxNGC_Event::ngch_syncmsg)
+	;
 }
 
 float ZoxNGCHistorySync::tick(float delta) {
diff --git a/src/solanaceae/zox/ngc_hs.hpp b/src/solanaceae/zox/ngc_hs.hpp
index 2d53d0a..e3b2b06 100644
--- a/src/solanaceae/zox/ngc_hs.hpp
+++ b/src/solanaceae/zox/ngc_hs.hpp
@@ -15,12 +15,13 @@ struct ToxI;
 struct ContactModelI;
 class ToxContactModel2;
 
-// zoff ngc history sync (draft1?)
-// https://gist.github.com/zoff99/81917ddb2e55b2ce602cac4772a7b68c
+// zoff ngc history sync
+// https://github.com/zoff99/c-toxcore/blob/zoff99/zoxcore_local_fork/docs/ngc_group_history_sync.md
+// (old) https://gist.github.com/zoff99/81917ddb2e55b2ce602cac4772a7b68c
 
 class ZoxNGCHistorySync : public ToxEventI, public ZoxNGCEventI {
-	ToxEventProviderI& _tep;
-	ZoxNGCEventProviderI& _zngcepi;
+	ToxEventProviderI::SubscriptionReference _tep_sr;
+	ZoxNGCEventProviderI::SubscriptionReference _zngcepi_sr;
 	ToxI& _t;
 	Contact3Registry& _cr;
 	ToxContactModel2& _tcm;
@@ -61,10 +62,6 @@ class ZoxNGCHistorySync : public ToxEventI, public ZoxNGCEventI {
 	};
 	std::map<Contact3, SyncQueueInfo> _sync_queue;
 
-	// sync queue
-
-	void subscribeToEvents(void); // private
-
 	public:
 		ZoxNGCHistorySync(ToxEventProviderI& tep, ZoxNGCEventProviderI& zngcepi, ToxI& t, Contact3Registry& cr, ToxContactModel2& tcm, RegistryMessageModelI& rmm);