Typed states for the displayed outbound observations.
Source: paper_references, paper_reference_links, observed 2026-08-16T10:30:38.827207Z
Paper Citation Record · LEDGER
Joint Resource Estimation and Trajectory Optimization for eVTOL-involved CR network: A Monte Carlo Tree Search-based Approach
As of 21 August 2026, this Paper Citation Record lists 39 of 39 outbound references and 0 inbound Pith citation observations for arXiv:2504.18031.
A citation records a reference. It does not transfer a finding from one paper to another.
Coverage vector
One-hop event checks from named stored sources.
Source: scholarly_work_events, retraction_status_cache, observed 2026-08-20T06:33:59.587034+00:00
Pith citing papers itemized under the disclosed page cap.
Source: paper_references, paper_reference_links
A source-named dated measurement, never combined with another source.
Source: cited_works
Reference resolution
39 of 39 outbound references displayed
- verified exact1
- verified fuzzy36
- unresolved2
- parse uncertain0
- malformed identifier0
- metadata mismatch0
External citation measurements
No source-named external measurement is stored.
Outbound references
Observation a59ce705-9729-4795-9763-f5418da9d561 · outbound
This paper cites NASA concept vehicles and the engineering of advanced air mobility aircraft,.
Joint Resource Estimation and Trajectory Optimization for eVTOL-involved CR network: A Monte Carlo Tree Search-based Approach NASA concept vehicles and the engineering of advanced air mobility aircraft,
Reference 1
- Resolution
- verified fuzzy
- raw_fallback, observed 2026-08-16T10:30:39.292559Z
Source-reported events for the cited work
No event found in the named queried sources as of 2026-08-20T06:33:59.587034+00:00.
Observation 41e6fec7-450f-4e28-8a52-b1c2f578b715 · outbound
This paper cites Advanced air mobility: An innovation for future diversified transportation and society,.
Joint Resource Estimation and Trajectory Optimization for eVTOL-involved CR network: A Monte Carlo Tree Search-based Approach Advanced air mobility: An innovation for future diversified transportation and society,
Reference 2
- Resolution
- verified fuzzy
- raw_fallback, observed 2026-08-16T10:30:39.281304Z
Source-reported events for the cited work
No event found in the named queried sources as of 2026-08-20T06:33:59.587034+00:00.
Observation 68492408-05cd-48a9-832a-abcedb34c103 · outbound
This paper cites Urban air mobility: His- tory, ecosystem, market potential, and challenges,.
Joint Resource Estimation and Trajectory Optimization for eVTOL-involved CR network: A Monte Carlo Tree Search-based Approach Urban air mobility: His- tory, ecosystem, market potential, and challenges,
Reference 3
- Resolution
- verified fuzzy
- raw_fallback, observed 2026-08-16T10:30:39.268763Z
Source-reported events for the cited work
No event found in the named queried sources as of 2026-08-20T06:33:59.587034+00:00.
Observation 58b7025f-c9df-4656-9e79-d51dc562b6a6 · outbound
This paper cites Advanced air mobility: Demand analysis and market potential of the airport shuttle and air taxi markets,.
Joint Resource Estimation and Trajectory Optimization for eVTOL-involved CR network: A Monte Carlo Tree Search-based Approach Advanced air mobility: Demand analysis and market potential of the airport shuttle and air taxi markets,
Reference 4
- Resolution
- verified fuzzy
- raw_fallback, observed 2026-08-16T10:30:39.251563Z
Source-reported events for the cited work
No event found in the named queried sources as of 2026-08-20T06:33:59.587034+00:00.
Observation 0e062b34-d712-400d-96f3-dc0727ddb1b2 · outbound
This paper cites Advanced air mobility: An innova- tion for future diversified transportation and society,.
Joint Resource Estimation and Trajectory Optimization for eVTOL-involved CR network: A Monte Carlo Tree Search-based Approach Advanced air mobility: An innova- tion for future diversified transportation and society,
Reference 5
- Resolution
- verified fuzzy
- raw_fallback, observed 2026-08-16T10:30:39.238743Z
Source-reported events for the cited work
No event found in the named queried sources as of 2026-08-20T06:33:59.587034+00:00.
Observation d228dfc5-8311-4c91-88fc-c07c5051a3cc · outbound
This paper cites Utilizing evtol aircraft to alleviate traffic congestion on an arterial road,.
Joint Resource Estimation and Trajectory Optimization for eVTOL-involved CR network: A Monte Carlo Tree Search-based Approach Utilizing evtol aircraft to alleviate traffic congestion on an arterial road,
Reference 6
- Resolution
- verified fuzzy
- raw_fallback, observed 2026-08-16T10:30:39.226308Z
Source-reported events for the cited work
No event found in the named queried sources as of 2026-08-20T06:33:59.587034+00:00.
Observation de5b68a9-e9d2-4de1-93b5-48f1be9c80d6 · outbound
This paper cites Roadmap AAM (2021-2030),.
Joint Resource Estimation and Trajectory Optimization for eVTOL-involved CR network: A Monte Carlo Tree Search-based Approach Roadmap AAM (2021-2030),
Reference 7
- Resolution
- unresolved
- no resolver link, observed 2026-08-16T10:30:38.709649Z
Source-reported events for the cited work
Unavailable: canonical work link unavailable.
Observation 89df45ad-3a0b-4efb-b3f1-fb0bf764c986 · outbound
This paper cites Au- tonomous navigation for eVTOL: Review and future perspectives,.
Joint Resource Estimation and Trajectory Optimization for eVTOL-involved CR network: A Monte Carlo Tree Search-based Approach Au- tonomous navigation for eVTOL: Review and future perspectives,
Reference 8
- Resolution
- unresolved
- no resolver link, observed 2026-08-16T10:30:38.713462Z
Source-reported events for the cited work
Unavailable: canonical work link unavailable.
Observation 93605e84-24ca-4446-8f03-904bbdfdd4a4 · outbound
This paper cites Dedicating cellular infras- tructure for aerial users: Advantages and potential impact on ground users,.
Joint Resource Estimation and Trajectory Optimization for eVTOL-involved CR network: A Monte Carlo Tree Search-based Approach Dedicating cellular infras- tructure for aerial users: Advantages and potential impact on ground users,
Reference 9
- Resolution
- verified fuzzy
- raw_fallback, observed 2026-08-16T10:30:39.201139Z
Source-reported events for the cited work
No event found in the named queried sources as of 2026-08-20T06:33:59.587034+00:00.
Observation fe6edde5-0e69-4387-9fe1-deefcf95818f · outbound
This paper cites Coverage analysis and trajec- tory optimization for aerial users with dedicated cellular infrastructure,.
Joint Resource Estimation and Trajectory Optimization for eVTOL-involved CR network: A Monte Carlo Tree Search-based Approach Coverage analysis and trajec- tory optimization for aerial users with dedicated cellular infrastructure,
Reference 10
- Resolution
- verified fuzzy
- raw_fallback, observed 2026-08-16T10:30:39.187416Z
Source-reported events for the cited work
No event found in the named queried sources as of 2026-08-20T06:33:59.587034+00:00.
Observation e10205d7-3836-49be-b0d6-fb78f23230fd · outbound
This paper cites Intelligent task offloading for heterogeneous v2x communications,.
Joint Resource Estimation and Trajectory Optimization for eVTOL-involved CR network: A Monte Carlo Tree Search-based Approach Intelligent task offloading for heterogeneous v2x communications,
Reference 11
- Resolution
- verified fuzzy
- raw_fallback, observed 2026-08-16T10:30:39.175731Z
Source-reported events for the cited work
No event found in the named queried sources as of 2026-08-20T06:33:59.587034+00:00.
Observation f23fb949-c0e4-4ccc-bbfd-b3c4b4443685 · outbound
This paper cites Machine learning predictions of lithium-ion battery state-of-health for eVTOL applications,.
Joint Resource Estimation and Trajectory Optimization for eVTOL-involved CR network: A Monte Carlo Tree Search-based Approach Machine learning predictions of lithium-ion battery state-of-health for eVTOL applications,
Reference 12
- Resolution
- verified fuzzy
- raw_fallback, observed 2026-08-16T10:30:39.165492Z
Source-reported events for the cited work
No event found in the named queried sources as of 2026-08-20T06:33:59.587034+00:00.
Observation 97fc3353-5650-4656-8587-1f3177c524bb · outbound
This paper cites Effects of range requirements and battery technology on electric VTOL sizing and operational performance,.
Joint Resource Estimation and Trajectory Optimization for eVTOL-involved CR network: A Monte Carlo Tree Search-based Approach Effects of range requirements and battery technology on electric VTOL sizing and operational performance,
Reference 13
- Resolution
- verified fuzzy
- raw_fallback, observed 2026-08-16T10:30:39.155680Z
Source-reported events for the cited work
No event found in the named queried sources as of 2026-08-20T06:33:59.587034+00:00.
Observation 9c12544a-4ffe-49d6-95a3-f1a39558a38f · outbound
This paper cites Performance evaluation of UA V-enabled cellular networks with battery-limited drones,.
Joint Resource Estimation and Trajectory Optimization for eVTOL-involved CR network: A Monte Carlo Tree Search-based Approach Performance evaluation of UA V-enabled cellular networks with battery-limited drones,
Reference 14
- Resolution
- verified fuzzy
- raw_fallback, observed 2026-08-16T10:30:39.144281Z
Source-reported events for the cited work
No event found in the named queried sources as of 2026-08-20T06:33:59.587034+00:00.
Observation 100ae119-7cfd-4f9f-a083-13e66fe36cb8 · outbound
This paper cites Joint mobility, communication and computation optimization for uavs in air-ground cooperative networks,.
Joint Resource Estimation and Trajectory Optimization for eVTOL-involved CR network: A Monte Carlo Tree Search-based Approach Joint mobility, communication and computation optimization for uavs in air-ground cooperative networks,
Reference 15
- Resolution
- verified fuzzy
- raw_fallback, observed 2026-08-16T10:30:39.133821Z
Source-reported events for the cited work
No event found in the named queried sources as of 2026-08-20T06:33:59.587034+00:00.
Observation 68295aec-50db-48d3-b92a-196a0d75e90a · outbound
This paper cites Tilt-wing eVTOL takeoff trajectory optimization,.
Joint Resource Estimation and Trajectory Optimization for eVTOL-involved CR network: A Monte Carlo Tree Search-based Approach Tilt-wing eVTOL takeoff trajectory optimization,
Reference 16
- Resolution
- verified fuzzy
- raw_fallback, observed 2026-08-16T10:30:39.123600Z
Source-reported events for the cited work
No event found in the named queried sources as of 2026-08-20T06:33:59.587034+00:00.
Observation f7ba0706-93fa-4274-9112-31efe99b6b18 · outbound
This paper cites Wind-optimal trajectories for multirotor eVTOL aircraft on uam missions,.
Joint Resource Estimation and Trajectory Optimization for eVTOL-involved CR network: A Monte Carlo Tree Search-based Approach Wind-optimal trajectories for multirotor eVTOL aircraft on uam missions,
Reference 17
- Resolution
- verified fuzzy
- raw_fallback, observed 2026-08-16T10:30:39.114093Z
Source-reported events for the cited work
No event found in the named queried sources as of 2026-08-20T06:33:59.587034+00:00.
Observation 3e37b2bb-93f9-4474-8526-e620bd0b3abe · outbound
This paper cites TEeVTOL: Balancing Energy and Time Efficiency in eVTOL Aircraft Path Planning Across City-Scale Wind Fields.
Joint Resource Estimation and Trajectory Optimization for eVTOL-involved CR network: A Monte Carlo Tree Search-based Approach TEeVTOL: Balancing Energy and Time Efficiency in eVTOL Aircraft Path Planning Across City-Scale Wind Fields
Reference 18
- Resolution
- verified exact
- local_arxiv, observed 2026-08-16T10:30:38.871722Z
Source-reported events for the cited work
No event found in the named queried sources as of 2026-08-20T06:33:59.587034+00:00.
Observation b9410c29-e41a-438a-a338-36f75c651c37 · outbound
This paper cites Energy efficiency enhanced landing strategy for manned eVTOLs using L1 adaptive control,.
Joint Resource Estimation and Trajectory Optimization for eVTOL-involved CR network: A Monte Carlo Tree Search-based Approach Energy efficiency enhanced landing strategy for manned eVTOLs using L1 adaptive control,
Reference 19
- Resolution
- verified fuzzy
- raw_fallback, observed 2026-08-16T10:30:39.104288Z
Source-reported events for the cited work
No event found in the named queried sources as of 2026-08-20T06:33:59.587034+00:00.
Observation 6efaf10f-e0ff-45ac-9b6e-df8fdec43bf4 · outbound
This paper cites Trajectory optimization for takeoff and landing phase of UAM considering energy and safety,.
Joint Resource Estimation and Trajectory Optimization for eVTOL-involved CR network: A Monte Carlo Tree Search-based Approach Trajectory optimization for takeoff and landing phase of UAM considering energy and safety,
Reference 20
- Resolution
- verified fuzzy
- raw_fallback, observed 2026-08-16T10:30:39.094021Z
Source-reported events for the cited work
No event found in the named queried sources as of 2026-08-20T06:33:59.587034+00:00.
Observation cf3d4819-952a-401a-84d0-a808b29fb891 · outbound
This paper cites Inverse machine learning prediction for optimal tilt-wing eVTOL takeoff trajectory,.
Joint Resource Estimation and Trajectory Optimization for eVTOL-involved CR network: A Monte Carlo Tree Search-based Approach Inverse machine learning prediction for optimal tilt-wing eVTOL takeoff trajectory,
Reference 21
- Resolution
- verified fuzzy
- raw_fallback, observed 2026-08-16T10:30:39.084218Z
Source-reported events for the cited work
No event found in the named queried sources as of 2026-08-20T06:33:59.587034+00:00.
Observation 83767d09-c4d5-4dec-8c67-1f9d6c1df288 · outbound
This paper cites Cognitive uav com- munication via joint maneuver and power control,.
Joint Resource Estimation and Trajectory Optimization for eVTOL-involved CR network: A Monte Carlo Tree Search-based Approach Cognitive uav com- munication via joint maneuver and power control,
Reference 22
- Resolution
- verified fuzzy
- raw_fallback, observed 2026-08-16T10:30:39.073720Z
Source-reported events for the cited work
No event found in the named queried sources as of 2026-08-20T06:33:59.587034+00:00.
Observation 09fdb709-33ca-4fe1-8366-4aa4ef3d0e26 · outbound
This paper cites Resource allocation in cognitive radio-enabled uav communication,.
Joint Resource Estimation and Trajectory Optimization for eVTOL-involved CR network: A Monte Carlo Tree Search-based Approach Resource allocation in cognitive radio-enabled uav communication,
Reference 23
- Resolution
- verified fuzzy
- raw_fallback, observed 2026-08-16T10:30:39.063643Z
Source-reported events for the cited work
No event found in the named queried sources as of 2026-08-20T06:33:59.587034+00:00.
Observation 9870386a-1457-40b9-9f0f-0ccfcfaae7b6 · outbound
This paper cites Joint 3D trajectory and resource optimization for a UA V relay-assisted cognitive radio network,.
Joint Resource Estimation and Trajectory Optimization for eVTOL-involved CR network: A Monte Carlo Tree Search-based Approach Joint 3D trajectory and resource optimization for a UA V relay-assisted cognitive radio network,
Reference 24
- Resolution
- verified fuzzy
- raw_fallback, observed 2026-08-16T10:30:39.054076Z
Source-reported events for the cited work
No event found in the named queried sources as of 2026-08-20T06:33:59.587034+00:00.
Observation dcd1c958-f6d4-44f5-8081-4b46fc0ebaf9 · outbound
This paper cites Joint optimization of trajectory and resource allocation for time- constrained UA V-enabled cognitive radio networks,.
Joint Resource Estimation and Trajectory Optimization for eVTOL-involved CR network: A Monte Carlo Tree Search-based Approach Joint optimization of trajectory and resource allocation for time- constrained UA V-enabled cognitive radio networks,
Reference 25
- Resolution
- verified fuzzy
- raw_fallback, observed 2026-08-16T10:30:39.045344Z
Source-reported events for the cited work
No event found in the named queried sources as of 2026-08-20T06:33:59.587034+00:00.
Observation 418399f1-a11c-4fb0-8ede-3468c0752928 · outbound
This paper cites When UA Vs meet cognitive radio: Offloading traffic under uncertain spectrum environment via deep reinforcement learning,.
Joint Resource Estimation and Trajectory Optimization for eVTOL-involved CR network: A Monte Carlo Tree Search-based Approach When UA Vs meet cognitive radio: Offloading traffic under uncertain spectrum environment via deep reinforcement learning,
Reference 26
- Resolution
- verified fuzzy
- raw_fallback, observed 2026-08-16T10:30:39.036746Z
Source-reported events for the cited work
No event found in the named queried sources as of 2026-08-20T06:33:59.587034+00:00.
Observation 50f07bbd-6fb4-4b6d-9d86-8d6a625d7eec · outbound
This paper cites Joint UA V trajectory and power allocation optimization for NOMA in cognitive radio network,.
Joint Resource Estimation and Trajectory Optimization for eVTOL-involved CR network: A Monte Carlo Tree Search-based Approach Joint UA V trajectory and power allocation optimization for NOMA in cognitive radio network,
Reference 27
- Resolution
- verified fuzzy
- raw_fallback, observed 2026-08-16T10:30:39.023753Z
Source-reported events for the cited work
No event found in the named queried sources as of 2026-08-20T06:33:59.587034+00:00.
Observation db18a0da-2afe-4540-b876-e440c8eb8c92 · outbound
This paper cites UA V- assisted secure communications in terrestrial cognitive radio networks: Joint power control and 3D trajectory optimization,.
Joint Resource Estimation and Trajectory Optimization for eVTOL-involved CR network: A Monte Carlo Tree Search-based Approach UA V- assisted secure communications in terrestrial cognitive radio networks: Joint power control and 3D trajectory optimization,
Reference 28
- Resolution
- verified fuzzy
- raw_fallback, observed 2026-08-16T10:30:39.012211Z
Source-reported events for the cited work
No event found in the named queried sources as of 2026-08-20T06:33:59.587034+00:00.
Observation e6837359-68c8-4137-9897-39a287f3bcaf · outbound
This paper cites Digital twin assisted deep reinforcement learning for computation offloading in uav systems,.
Joint Resource Estimation and Trajectory Optimization for eVTOL-involved CR network: A Monte Carlo Tree Search-based Approach Digital twin assisted deep reinforcement learning for computation offloading in uav systems,
Reference 29
- Resolution
- verified fuzzy
- raw_fallback, observed 2026-08-16T10:30:39.000089Z
Source-reported events for the cited work
No event found in the named queried sources as of 2026-08-20T06:33:59.587034+00:00.
Observation ca406b0e-3e9a-4795-9178-e241b9eb3075 · outbound
This paper cites Uav-assisted target tracking and computation offloading in usv-based mec networks,.
Joint Resource Estimation and Trajectory Optimization for eVTOL-involved CR network: A Monte Carlo Tree Search-based Approach Uav-assisted target tracking and computation offloading in usv-based mec networks,
Reference 30
- Resolution
- verified fuzzy
- raw_fallback, observed 2026-08-16T10:30:38.989380Z
Source-reported events for the cited work
No event found in the named queried sources as of 2026-08-20T06:33:59.587034+00:00.
Observation c4d2a278-2b9b-463b-9d4a-aa9e3b2bba1e · outbound
This paper cites Dronesegnet: Robust aerial semantic segmentation for uav- based iot applications,.
Joint Resource Estimation and Trajectory Optimization for eVTOL-involved CR network: A Monte Carlo Tree Search-based Approach Dronesegnet: Robust aerial semantic segmentation for uav- based iot applications,
Reference 31
- Resolution
- verified fuzzy
- raw_fallback, observed 2026-08-16T10:30:38.978896Z
Source-reported events for the cited work
No event found in the named queried sources as of 2026-08-20T06:33:59.587034+00:00.
Observation 0a6ef0f6-6cb9-4347-8a67-9d8601effd17 · outbound
This paper cites Energy efficient transmission strategy for mobile edge computing network in uav-based patrol inspection system,.
Joint Resource Estimation and Trajectory Optimization for eVTOL-involved CR network: A Monte Carlo Tree Search-based Approach Energy efficient transmission strategy for mobile edge computing network in uav-based patrol inspection system,
Reference 32
- Resolution
- verified fuzzy
- raw_fallback, observed 2026-08-16T10:30:38.968642Z
Source-reported events for the cited work
No event found in the named queried sources as of 2026-08-20T06:33:59.587034+00:00.
Observation a035ac4d-43e0-4d66-bef6-2f13dae74431 · outbound
This paper cites Joint multi-task offloading and resource allocation for mobile edge computing systems in satellite iot,.
Joint Resource Estimation and Trajectory Optimization for eVTOL-involved CR network: A Monte Carlo Tree Search-based Approach Joint multi-task offloading and resource allocation for mobile edge computing systems in satellite iot,
Reference 33
- Resolution
- verified fuzzy
- raw_fallback, observed 2026-08-16T10:30:38.958596Z
Source-reported events for the cited work
No event found in the named queried sources as of 2026-08-20T06:33:59.587034+00:00.
Observation 61530926-b0e4-468c-884a-fc4059004e3e · outbound
This paper cites Dynamic task offloading for multi-uavs in vehicular edge computing with delay guarantees: A consensus admm-based optimization,.
Joint Resource Estimation and Trajectory Optimization for eVTOL-involved CR network: A Monte Carlo Tree Search-based Approach Dynamic task offloading for multi-uavs in vehicular edge computing with delay guarantees: A consensus admm-based optimization,
Reference 34
- Resolution
- verified fuzzy
- raw_fallback, observed 2026-08-16T10:30:38.948308Z
Source-reported events for the cited work
No event found in the named queried sources as of 2026-08-20T06:33:59.587034+00:00.
Observation af446b8a-0a95-4036-b1f6-0d875c0b5d04 · outbound
This paper cites Two-stage deep energy optimization in irs-assisted uav-based edge computing systems,.
Joint Resource Estimation and Trajectory Optimization for eVTOL-involved CR network: A Monte Carlo Tree Search-based Approach Two-stage deep energy optimization in irs-assisted uav-based edge computing systems,
Reference 35
- Resolution
- verified fuzzy
- raw_fallback, observed 2026-08-16T10:30:38.938157Z
Source-reported events for the cited work
No event found in the named queried sources as of 2026-08-20T06:33:59.587034+00:00.
Observation adcdca92-ca03-4b49-914d-44ea98b50c7d · outbound
This paper cites Analytical evaluation of outage probabil- ity based on signal to interference ratio for gaussian-distributed users,.
Joint Resource Estimation and Trajectory Optimization for eVTOL-involved CR network: A Monte Carlo Tree Search-based Approach Analytical evaluation of outage probabil- ity based on signal to interference ratio for gaussian-distributed users,
Reference 36
- Resolution
- verified fuzzy
- raw_fallback, observed 2026-08-16T10:30:38.926744Z
Source-reported events for the cited work
No event found in the named queried sources as of 2026-08-20T06:33:59.587034+00:00.
Observation 6e2ed35b-db38-4c56-be42-4240e3c35103 · outbound
This paper cites Uav-enabled wireless power transfer with base station charging and uav power consumption,.
Joint Resource Estimation and Trajectory Optimization for eVTOL-involved CR network: A Monte Carlo Tree Search-based Approach Uav-enabled wireless power transfer with base station charging and uav power consumption,
Reference 37
- Resolution
- verified fuzzy
- raw_fallback, observed 2026-08-16T10:30:38.912714Z
Source-reported events for the cited work
No event found in the named queried sources as of 2026-08-20T06:33:59.587034+00:00.
Observation 13cb30f9-b5a3-49d1-8f1c-0704cb0f807a · outbound
This paper cites Sample-efficient neural architecture search by learning actions for monte carlo tree search,.
Joint Resource Estimation and Trajectory Optimization for eVTOL-involved CR network: A Monte Carlo Tree Search-based Approach Sample-efficient neural architecture search by learning actions for monte carlo tree search,
Reference 38
- Resolution
- verified fuzzy
- raw_fallback, observed 2026-08-16T10:30:38.898895Z
Source-reported events for the cited work
No event found in the named queried sources as of 2026-08-20T06:33:59.587034+00:00.
Observation 59bc6957-a1b3-4a8d-91af-a1cb61c17ecd · outbound
This paper cites Bandit based monte-carlo planning,.
Joint Resource Estimation and Trajectory Optimization for eVTOL-involved CR network: A Monte Carlo Tree Search-based Approach Bandit based monte-carlo planning,
Reference 39
- Resolution
- verified fuzzy
- raw_fallback, observed 2026-08-16T10:30:38.886040Z
Source-reported events for the cited work
No event found in the named queried sources as of 2026-08-20T06:33:59.587034+00:00.
Pith citing papers
No inbound Pith citation observations are available.